Solution: In determine if the variable is qualitative or

Problem 1AYU Define the following: (a) Experimental unit ________________ (b) Treatment ________________ (c) Response variable ________________ (d) Factor ________________ (e) Placebo ________________ (f ) Confounding

Problem 1CT List the four components that comprise the definition of statistics.

In Problems Provide a definition using your own words. Statistics

Problem 2AYU What is replication in an experiment?

Problem 2CT What is meant by the process of statistics?

Problem 2RE In Problems Provide a definition using your own words. Population

Explain the difference between a single-blind and a double blind experiment.

Problem 3CT In Problems determine if the variable is qualitative or quantitative. If the variable is quantitative, determine if it is discrete or continuous. State the level of measurement of the variable. Time to complete the 500-meter race in speed skating.

In Problems 1-5, provide a definition using your own words. Sample

Problem 4AYU A(n) ______ ______ design is one in which each experimental unit is randomly assigned to a treatment. A(n) ______ ______ design is one in which the experimental units are paired up.

In Problems 3-5, determine if the variable is qualitative or quantitative. If the variable is quantitative, determine if it is discrete or continuous. State the level of measurement of the variable. Video game rating system by the Entertainment Software Rating Board (EC, E, E10+, T, M, AO, RP)

In Problems 1-5, provide a definition using your own words. Observational study

Problem 5AYU True or False:Observational studies are used to determine causality between explanatory and response variables.

In Problems 3-5, determine if the variable is qualitative or quantitative. If the variable is quantitative, determine if it is discrete or continuous. State the level of measurement of the variable. The number of surface imperfections on a camera lens.

Provide a definition using your own words. Designed experiment

Problem 6AYU True or False: Generally, the goal of an experiment is to determine the effect that treatments will have on the response variable.

Problem 6CT In Problems, determine whether the study depicts an observational study or a designed experiment. Identify the response variable in each case. A random sample of 30 digital cameras is selected and divided into two groups. One group uses a brand-name battery, while the other uses a generic plain-label battery. All variables besides battery type are controlled. Pictures are taken under identical conditions and the battery life of the two groups is compared.

List and describe the three major types of observational studies.

Caffeinated Sports Drinks Researchers conducted a doubleblind, placebo-controlled,repeated-measures experiment to compare the effectiveness of a commercial caffeinated carbohydrate–electrolyte sports drink with a commercial noncaffeinated carbohydrate–electrolyte sports drink and a flavored-water placebo. Sixteen highly trained cyclists each completed three trials of prolonged cycling in a warm environment: one while receiving the placebo, one while receiving the noncaffeinated sports drink, and one while receiving the caffeinated sports drink. For a given trial, one beverage treatment was administered throughout a 2-hour variable-intensity cycling bout followed by a 15-minute performance ride. Total work in kilojoules (kJ) performed during the final 15 minutes was used to measure performance. The beverage order for the individual subjects was randomly assigned. A period of at least 5 days separated the trials. All trials took place at approximately the same time of day in an environmental chamber at 28.5°C and 60% relative humidity with fan airflow of approximately 2.5 meters per second (m/s). The researchers found that cycling performance, as assessed by the total work completed during the performance ride, was 23% greater for the caffeinated sports drink than for the placebo and 15% greater for the caffeinated sports drink than for the noncaffeinated sports drink. Cycling performances for the noncaffeinated sports drink and the placebo were not significantly different. The researchers concluded that the caffeinated carbohydrate–electrolyte sports drink substantially enhanced physical performance during prolonged exercise compared with the noncaffeinated carbohydrate–electrolyte sports drink and the placebo. Source: Kirk J. Cureton, Gordon L. Warren et al. “Caffeinated Sports Drink: Ergogenic Effects and Possible Mechanisms,” International Journal of Sport Nutrition and Exercise Metabolism, 17(1):35–55, 2007 (a) What does it mean for the experiment to be placebo-controlled? (b) What does it mean for the experiment to be double-blind? Why do you think it is necessary for the experiment to be double-blind? (c) How is randomization used in this experiment? (d) What is the population for which this study applies? What is the sample? (e) What are the treatments? (f ) What is the response variable? (g) This experiment used a repeated-measures design, a design type that has not been directly discussed in this textbook. Using this experiment as a guide, determine what it means for the design of the experiment to be repeated-measures. How does this design relate to the matched-pairs design?

In Problems 6 and 7, determine whether the study depicts an observational study or a designed experiment. Identify the response variable in each case. A sports reporter asks 100 baseball fans if Barry Bonds’s 756th home run ball should be marked with an asterisk when sent to the Baseball Hall of Fame.

What is meant by the process of statistics?

Alcohol Dependence To determine if topiramate is a safe and effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this double-blind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. Source: Bankole A. Johnson, Norman Rosenthal, et al. “Topiramate for Treating Alcohol Dependence: A Randomized Controlled Trial,” Journal of the American Medical Association, 298(14):1641–1651, 2007 (a) What does it mean for the experiment to be placebo-controlled? (b) What does it mean for the experiment to be double-blind? Why do you think it is necessary for the experiment to be double-blind? (c) What does it mean for the experiment to be randomized? (d) What is the population for which this study applies? What is the sample? (e) What are the treatments? (f) What is the response variable?

Problem 8CT Contrast the three major types of observational studies in terms of the time frame when the data are collected.

Problem 8RE List and explain the three sources of bias in sampling. Provide some methods that might be used to minimize bias in sampling.

School Psychology A school psychologist wants to test the effectiveness of a new method for teaching reading. She recruits 500 first-grade students in District 203 and randomly divides them into two groups. Group 1 is taught by means of the new method, while group 2 is taught by traditional methods. The same teacher is assigned to teach both groups. At the end of the year, an achievement test is administered and the results of the two groups are compared. (a) What is the response variable in this experiment? (b)Think of some of the factors in the study. How are they controlled? (c) What are the treatments? How many treatments are there? (d) How are the factors that are not controlled dealt with? (e)Which group serves as the control group? (f)What type of experimental design is this? (g)Identify the subjects. (h) Draw a diagram similar to Figure 7 or 8 to illustrate the design.

Compare and contrast observational studies and designed experiments. Which study allows a researcher to claim causality?

Distinguish between sampling and nonsampling error.

Problem 10AYU Pharmacy A pharmaceutical company has developed an experimental drug meant to relieve symptoms associated with the common cold. Hie company identifies 300 adult males 25 to 29 years old who have a common cold and randomly divides them into two groups. Group 1 is given the experimental drug, while group 2 is given a placebo. After 1 week of treatment, the proportions of each group that still have cold symptoms are compared. (a)What is the response variable in this experiment? ________________ (b)Think of some of the factors in the study. How are they controlled? ________________ (c)What are the treatments? How many treatments are there? ________________ (d) How are the factors that are not controlled dealt with? ________________ (e)What type of experimental design is this? ________________ (f) Identify the subjects. ________________ (g)Draw a diagram similar to Figure 7 or 8 to illustrate the design.

Explain why it is important to use a control group and blinding in an experiment.

Explain the steps in designing an experiment.

Problem 11AYU Whiter Teeth An ad for Crest Whitestrips Premium claims that the strips will whiten teeth in 7 days and the results will last for 12 months. A researcher who wishes to test this claim studies 20 sets of identical twins. Within each set of twins, one is randomly selected to use Crest Whitestrips Premium in addition to regular brushing and flossing, while the other just brushes and flosses. Whiteness of teeth is measured at the beginning of the study, after 7 days, and every month thereafter for 12 months. (a) What type of experimental design is this? ________________ (b) What is the response variable in this experiment? ________________ (c) What are the treatments? ________________ (d) What are other factors (controlled or uncontrolled) that could affect the response variable? ________________ (e) What might be an advantage of using identical twins as subjects in this experiment?

List the steps required to conduct an experiment.

Problem 11RE In Problems classify the variable as qualitative or quantitative. If the variable is quantitative, state whether it is discrete or continuous. Number of new automobiles sold at a dealership on a given day

Problem 12AYU Assessment To help assess student learning in her developmental math courses, a mathematics professor at a community college implemented pre- and posttests for herstudents. A knowledge-gained score was obtained by taking the difference of the two test scores. (a) What type of experimental design is this? ________________ (b) What is the response variable in this experiment? ________________ (c) What is the treatment?

Problem 12CT A cellular phone company is looking for ways to improve customer satisfaction. They want to select a simple random sample of four stores from their 15 franchises in which to conduct customer satisfaction surveys. Discuss the procedure you would use, and then use the procedure to select a simple random sample of size n = 4. The locations are as follows:

In Problems 11-13, classify the variable as qualitative or quantitative. If the variable is quantitative, state whether it is discrete or continuous Weight in carats of an uncut diamond

Insomnia Researchers Jack D. Edinger and associates wanted to test the effectiveness of a new cognitive behavioral therapy (CBT) compared with both an older behavioral treatment and a placebo therapy for treating insomnia. They identified 75 adults with chronic insomnia. Patients were randomly assigned to one of three treatment groups. Twenty-five patients were randomly assigned to receive CBT (sleep education, stimulus control, and time-in-bed restrictions), another 25 received muscle relaxation training (RT), and the final 25 received a placebo treatment. Treatment lasted 6 weeks, with follow-up conducted at 6 months. To measure the effectiveness of the treatment, researchers used wake time after sleep onset (WASO). Cognitive behavioral therapy produced larger improvements than did RT or placebo treatment. For example, the CBT-treated patients achieved an average 54% reduction in their WASO, whereas RT-treated and placebo-treated patients, respectively, achieved only 16% and 12% reductions in this measure. Results suggest that CBT treatment leads to significant sleep improvements within 6 weeks, and these improvements appear to endure through 6months of follow-up.Source: Jack D. Edinger, PhD; William K. Wohlgemuth, PhD; Rodney A. Radtke, MD; Gail R. Marsh, PhD; Ruth E. Quillian, PhD. “Cognitive Behavioral Therapy for Treatment of Chronic PrimaryInsomnia,”Journal of the American Medical Association 285:185-1864,2001 (a) What type of experimental design is this? (b) What is the population being studied? (c) What is the response variable in this study? (d) What are the treatments? (e) Identify the experimental units. (f) Draw a diagram similar to Figure 7 or 8 to illustrate the design.

Problem 13CT A congresswoman wants to survey her constituency regarding public policy. She asks one of her staff members to obtain a sample of residents of the district. The frame she has available lists 9012 Democrats, 8302 Republicans, and 3012 Independents. Obtain a stratified random sample of 8 Democrats, 7 Republicans, and 3 Independents. Be sure to discuss the procedure used.

Classify the variable as qualitative or quantitative. If the variable is quantitative, state whether it is discrete or continuous Brand name of a pair of running shoes

Depression Researchers wanted to compare the effectiveness and safety of an extract of St. John’s wort with placebo in outpatients with major depression. To do this, they recruited 200 adult outpatients diagnosed as having major depression and having a baseline Hamilton Rating Scale for Depression (HAM-D) score of at least 20. Participants were randomly assigned to receive either St. John’s wort extract, 900milligrams per day (mg/d) for 4 weeks, increased to 1200 mg/d in the absence of an adequate response thereafter, or a placebo for 8 weeks. The response variable was the change on the HAM-D over the treatment period. After analysis of the data, it was concluded that St. John’s wort was not effective for treatment of major depression.Source: Richard C. Shelton, MD, et al. “Effectiveness of St. John’s Wort in Major Depression,”Journal of the American Medical Association 285:1978-1986,2001 (a)What type of experimental design is this? (b)What is the population that is being studied? (c) What is the response variable in this study? (d) What are the treatments? (e)Identify the experimental units. (f) What is the control group in this study? (g)Draw a diagram similar to Figure 7 or 8 to illustrate the design.

Problem 14CT A farmer has a 500-acre orchard in Florida. Each acre is subdivided into blocks of 5. Altogether, there are 2500 blocks of trees on the farm. After a frost, he wants to get an idea of the extent of the damage. Obtain a sample of 10 blocks of trees using a cluster sample. Be sure to discuss the procedure used.

Determine whether the underlined value is a parameter or a statistic. In a survey of 1011 people age 50 or older, 73% agreed with the statement “I believe in life after death.” Source: Bill Newcott. “Life after Death,” AARP Magazine, Sept./Oct. 2007

Problem 15AYU The Memory Drug? Researchers wanted to evaluate whether ginkgo, an over-the-counter herb marketed as enhancing memory, improves memory in elderly adults as measured by objective tests. To do this, they recruited 98 men and 132 women older than 60 years and in good health. Participants were randomly assigned to receive ginkgo, 40 milligrams (mg) 3 times per day, or a matching placebo. The measure of memory improvement was determined by a standardized test of learning and memory. After 6 weeks of treatment, the data indicated that ginkgo did not increase performance on standard tests of learning, memory, attention, and concentration. These data suggest that, when taken following the manufacturer’s instructions, ginkgo provides no measurable increase in memory or related cognitive function to adults with healthy cognitive function.Source:Paul R. Solomon et al. “Ginkgo for Memory Enhancement,”Journal of the American Medical Association288:835-840,2002 (a)What type of experimental design is this? ________________ (b)What is the population being studied? ________________ (c)What is the response variable in this study? ________________ (d) What is the factor that is set to predetermined levels? What are the treatments? ________________ (e)Identify the experimental units. ________________ (f) What is the control group in this study? ________________ (g)Draw a diagram similar to Figure 7 or 8 to illustrate the design.

A casino manager wants to inspect a sample of 14 slot machines in his casino for quality-control purposes. There are 600 sequentially numbered slot machines operating in the casino. Obtain a systematic sample of 14 slot machines. Be sure to discuss how you obtained the sample.

Problem 15RE In Problems Determine whether the underlined value is a parameter or a statistic. Completion Rate In the 2011 NCAA Football Championship Game, quarterback Cam Newton completed 59% of his passes for a total of 265 yards and 2 touchdowns.

Shrinking Stomach? Researchers wanted to determine whether the stomach shrinks as a result of dieting. To do this, they randomly divided 23 obese patients into two groups. The 14 individuals in the experimental group were placed on a diet that allowed them to consume 2508 kilojoules (kJ) per day for 4 weeks. The 9 subjects in the control group ate as they normally would. To assess the size of the stomach, a latex gastric balloon was inserted into each subject’s stomach and filled with the maximum amount of water that could be tolerated by the patient. The volume of water was compared to the volume that could be tolerated at the beginning of the study. The experimental subjects experienced a 27% reduction in gastric capacity, while the subjects in the control group experienced no change in gastric capacity. It was concluded that a reduction in gastric capacity occurs after a restricted diet.Source:A. Geliebteret al. “Reduced Stomach Capacity in Obese Subjects after Dieting,”American Journal of Clinical Nutrition63(2):170-173,1996 (a) What type of experimental design is this? (b) What is the population that the results of this experiment apply to? (c) What is the response variable in this study? Is it qualitative or quantitative? (d) What are the treatments? (e) Identify the experimental units. (f) Draw a diagram similar to Figure 7 or 8 to illustrate the design.

Describe what is meant by an experiment that has a completely randomized design. Contrast this experimental design with a randomized block design.

In Problems 16-19, determine the level of measurement of each variable. Birth year

Problem 17AYU Dominant HandProfessor Andy Neill wanted to determine if the reaction time of people differs in their dominant hand versus their nondominant hand. To do this, he recruited 15 students. Each student was asked to hold a yardstick between the index finger and thumb. The student was asked to open the hand, release the yardstick, and then asked to catch the yardstick between the index finger and thumb.The distance that the yardstick fell served as a measure of reaction time. A coin flip was used to determine whether the student would use their dominant hand first or the nondominant hand. Results indicated that the reaction time in the dominant hand exceeded that of the nondominant hand. (a)What type of experimental design is this? ________________ (b)What is the response variable in this study? ________________ (c)What is the treatment? ________________ (d)Identify the experimental units. ________________ (e)Why did Professor Neill use a coin flip to determine whether the student should begin with the dominant hand or the nondominant hand? ________________ (f)Draw a diagram similar to Figure7or 8 to illustrate the design.

Each of the following surveys has bias. Identify the type of bias. (a) A television survey that gives 900 phone numbers for viewers to call with their vote. Each call costs $2.00. (b) An employer distributes a survey to her 450 employees asking them how many hours each week, on average, they surf the Internet during business hours. Three of the employees complete the survey. (c) A question on a survey asks, “Do you favor or oppose a minor increase in property tax to ensure fair salaries for teachers and properly equipped school buildings?” (d) A researcher conducting a poll about national politics sends a survey to a random sample of subscribers to Time magazine.

In Problems 16-19, determine the level of measurement of each variable. Marital status

Golf Anyone? A local golf pro wanted to compare two styles of golf club. One golf club had a graphite shaft and the other had the latest style of steel shaft. It is a common belief that graphite shafts allow a player to hit the ball farther, but the manufacturer of the new steel shaft said the ball travels just as far with its new technology. To test this belief, the pro recruited 10 golfers from the driving range. Each player was asked to hit one ball with the graphite-shafted club and one ball with the new steel-shafted club. The distance that the ball traveled was determined using a range finder. A coin flip was used to determine whether the player hit with the graphite club or the steel club first. Results indicated that the distance the ball was hit with the graphite club was no different than the distance when using the steel club. (a) What type of experimental design is this? (b) What is the response variable in this study? (c) What is the factor that is set to predetermined levels? What is the treatment? (d) Identify the experimental units. (e) Why did the golf pro use a coin flip to determine whether the golfer should hit with the graphite first or the steel first? (f) Draw a diagram similar to Figure 7 or 8 to illustrate the design.

Problem 18CT The four members of Skylab had their lymphocyte count per cubic millimeter measured 1 day before lift-off and measured again on their return to Earth. (a)What is the response variable in this experiment? ________________ (b)What is the treatment? ________________ (c)What type of experimental design is this? ________________ (d)Idehtify the experimental units. ________________ (e) Draw a diagram similar to Figure 7 or 8 to illustrate the design. ________________

Problem 18RE In Problems Determine the level of measurement of each variable. Stock rating (strong buy, buy, hold, sell, strong sell)

Problem 19AYU Drug Effectiveness A pharmaceutical company wants to test the effectiveness of an experimental drug meant to reduce high cholesterol. The researcher at the pharmaceutical company has decided to test the effectiveness of the drug through a completely randomized design. She has obtained 20 volunteers with high cholesterol: Ann, John, Michael, Kevin, Marissa, Christina, Eddie, Shannon, Julia, Randy, Sue, Tom, Wanda, Roger, Laurie, Rick, Kim, Joe, Colleen, and Bill. Number the volunteers from 1 to 20. Use a random-number generator to randomly assign 10 of the volunteers to the experimental group. The remaining volunteers will go into the control group. List the individuals in each group.

Problem 19CT Nucryst Pharmaceuticals, Inc., announced the results of its first human trial of NPI32101, a topical form of its skin ointment. A total of 225 patients diagnosed with skin irritations were randomly divided into three groups as part of a double-blind, placebo-controlled study to test the effectiveness of the new topical cream.The first group received a 0.5% cream, the second group received a 1.0% cream, and the third group received a placebo. Groups were treated twice daily for a 6-week period.Source:www.nucryst.com (a)What type of experimental design is this? ________________ (b)What is the response variable in this experiment? ________________ (c)What is the factor that is set to predetermined levels? Win at are the treatments? ________________ (d)What does it mean for this study to be double-blind? ________________ (e) What is the control group for this study? ________________ (f)Identify the experimental units. ________________ (g)Draw a diagram similar to Figure 7 or 8 to illustrate the design.

In Problems 16-19, determine the level of measurement of each variable. Number of siblings

Effects of Alcohol A researcher has recruited 20 volunteers to participate in a study. The researcher wishes to measure the effect of alcohol on an individual’s reaction time. The 20 volunteers are randomly divided into two groups. Group 1 serves as a control group in which participants drink four 1-ounce cups of a liquid that looks, smells, and tastes like alcohol in 15-minute increments. Group 2 will serve as an experimental group in which participants drink four 1-ounce cups of 80-proof alcohol in 15-minute increments. After drinking the last 1-ounce cup, the participants sit for 20 minutes. After the 20-minute resting period, the reaction time to a stimulus is measured. (a) What type of experimental design is this? (b) Use Table I in Appendix A or a random-number generator to divide the 20 volunteers into groups 1 and 2 by assigning the volunteers a number between 1 and 20. Then randomly select 10 numbers between 1 and 20. The individuals corresponding to these numbers will go into group 1.

Determine whether the study depicts an observational study or a designed experiment. A parent group examines 25 randomly selected PG-13 movies and 25 randomly selected PG movies and records the number of sexual innuendos and curse words that occur in each. They then compare the number of sexual innuendos and curse words between the two movie ratings.

Tomatoes An oncologist wants to perform a long-term study on the benefits of eating tomatoes. In particular, she wishes to determine whether there is a significant difference in the rate of prostate cancer among adult males after eating one serving of tomatoes per week for 5 years, after eating three servings of tomatoes per week for 5 years, and after eating five servings of tomatoes per week for 5 years. Help the oncologist design the experiment. Include a diagram to illustrate your design.

Problem 21RE In Problems, determine whether the study depicts an observational study or a designed experiment. A sample of 504 patients in early stages of Alzheimer’s disease is divided into two groups. One group receives an experimental drug; the other receives a placebo. The advance of the disease in the patients from the two groups is tracked at 1-month intervals over the next year.

Batteries An engineer wants to determine the effect of temperature on battery voltage. In particular, he is interested in determining if there is a significant difference in the voltage of the batteries when exposed to temperatures of \(\mathrm {90^\circ \mathrm F, 70^\circ F}\) and \(50^\circ \mathrm F\). Help the engineer design the experiment. Include a diagram to illustrate your design.

Read the following description of an observational study and determine whether it is a cross-sectional, a case-control, or a cohort study. Explain your choice. The Cancer Prevention Study II (CPS-II) examines the relationship among environmental and lifestyle factors of cancer cases by tracking approximately 1.2 million men and women. Study participants completed an initial study questionnaire in 1982 providing information on a range of lifestyle factors, such as diet, alcohol and tobacco use, occupation, medical history, and family cancer history. These data have been examined extensively in relation to cancer mortality. The vital status of study participants is updated biennially. Source: American Cancer Society

The Better Paint Suppose you are interested in comparing Benjamin Moore’s MoorLife Latex house paint with Sherwin Williams’ LowTemp 35 Exterior Latex paint. Design an experiment that will answer this question: Which paint is better for painting the exterior of a house? Include a diagram to illustrate your design.

Problem 23RE In Problems, determine the type of sampling used. On election day, a pollster for Fox News positions herself outside a polling place near her home. She then asks the first 50 voters leaving the facility to complete a survey.

Problem 24AYU Tire Design An engineer has just developed a new tire design. However, before going into production, the tire company wants to determine if the new tire reduces braking distance on a car traveling 60 miles per hour compared with radial tires. Design an experiment to help the engineer determine if the new tire reduces braking distance.

Determine the type of sampling used. An Internet service provider randomly selects 15 residential blocks from a large city. It then surveys every household in these 15 blocks to determine the number that would use a high-speed Internet service if it were made available.

Problem 25AYU Designing an Experiment Researchers wish to know if there is a link between hypertension (high blood pressure) and consumption of salt. Past studies have indicated that the consumption of fruits and vegetables offsets the negative impact of salt consumption. It is also known that there is quite a bit of person-to-person variability as far as the ability of the body to process and eliminate salt. However, no method exists for identifying individuals who have a higher ability to process salt. The U.S. Department of Agriculture recommends that daily intake of salt should not exceed 2400 milligrams (mg).m The researchers want to keep the design simple, so they choose to conduct their study using a completely randomized design. (a) What is the response variable in the study? ________________ (b) Name three factors that have been identified. ________________ (c) For each factor identified, determine whether the variable can be controlled or cannot be controlled. If a factor cannot be controlled, what should be done to reduce variability in the response variable? ________________ (d) How many treatments would you recommend? Why?

Problem 26AYU Search a newspaper, magazine, or other periodical that describes an experiment. Identify the population, experimental unit, response variable, treatment, factors, and their levels.

Problem 26RE In Problems, determine the type of sampling used. Officers for the Department of Motor Vehicles pull aside every 40th tractor trailer passing through a weigh station, starting with the 12th, for an emissions test.

Problem 27AYU Research the placebo effect and the Hawthorne effect. Write a paragraph that describes how each affects the outcome of an experiment.

Problem 27RE Each of the following surveys has bias. Determine the type of bias and suggest a remedy. (a) A politician sends a survey about tax issues to a random sample of subscribers to a literary magazine. ________________ (b) An interviewer with little foreign language knowledge is sent to an area where her language is not commonly spoken. ________________ (c) A data-entry clerk mistypes survey results into his computer.

Problem 28AYU Coke or Pepsi Suppose you want to perform an experiment whose goal is to determine whether people prefer Coke or Pepsi. Design an experiment that utilizes the completely randomized design. Design an experiment that utilizes the matched-pairs design. In both designs, be sure to identify the response variable, the role of blinding, and randomization. Which design do you prefer? Why?

Problem 28RE Obtaining a Simple Random Sample The mayor of a small town wants to conduct personal interviews with small business owners to determine if there is anything the mayor could do to help improve business conditions. The following list gives the names of the companies in the town. Obtain a simple random sample of size 5 from the companies in the town.

Putting It Together: Mosquito Control In an attempt to identify ecologically friendly methods for controlling mosquito populations, researchers conducted field experiments in India where aquatic nymphs of the dragonfly Brachytron pretense were used against the larvae of mosquitoes. For the experiment, the researchers selected ten 300-liter (L) outdoor, open, concrete water tanks, which were natural breeding places for mosquitoes. Each tank was manually sieved to ensure that it was free of any nonmosquito larvae, nymphs, or fish. Only larvae of mosquitoes were allowed to remain in the tanks. The larval density in each tank was assessed using a 250-milliliter (ml) dipper. For each tank, 30 dips were taken and the mean larval density per dip was calculated. Ten freshly collected nymphs of Brachytron pretense were introduced into each of five randomly selected tanks. No nymphs were released into the remaining five tanks, which served as controls. After 15 days, larval densities in all the tanks were assessed again and all the introduced nymphs were removed. After another 15 days, the larval densities in all the tanks were assessed a third time. In the nymph-treated tanks, the density of larval mosquitoes dropped significantly from 7.34 to 0.83 larvae per dip 15 days after the Brachytron pretense nymphs were introduced. Further, the larval density increased significantly to 6.83 larvae per dip 15 days after the nymphs were removed. Over the same time period, the control tanks did not show a significant difference in larval density, with density measurements of 7.12, 6.83, and 6.79 larvae per dip. The researchers concluded that Brachytron pretense can be used effectively as a strong, ecologically friendly control of mosquitoes and mosquito-borne diseases.Source:S. N. Chatterjee,A.Ghosh, and G.Chandra. “Eco-Friendly Control of Mosquito Larvae by Brachytron pretense Nymph,”Journal of Environmental Health 69(8): 44-48,2007 (a) Identify the research objective. (b) What type of experimental design is this? (c) What is the response variable? Is it quantitative or qualitative? If quantitative, is it discrete or continuous? (d) What is the factor the researchers controlled and set to predetermined levels? What are the treatments? (e) Can you think of other factors that may affect larvae of mosquitoes? How are they controlled or dealt with? (f) What is the population for which this study applies? What is the sample? (g) List the descriptive statistics. (h) How did the researchers control this experiment? (i) Draw a diagram similar to Figure 7 or 8 to illustrate the design. (j) State the conclusion made in the study.

Obtaining a Systematic Sample A quality-control engineer wants to be sure that bolts coming off an assembly line are within prescribed tolerances. He wants to conduct a systematic sample by selecting every 9th bolt to come off the assembly line. The machine produces 30,000 bolts per day, and the engineer wants a sample of 32 bolts. Which bolts will be sampled?

Problem 30AYU The Dictator Game In their book SuperFreakonomics, authors Steven Levitt and Stephen Dubner describe the research of behavioral economist John List. List recruited customers and dealers at a baseball-card show to participate in an experiment in which the customer would state how much he was willing to pay for a single baseball card. The prices ranged from $4 (lowball) to $50 (premium card). The dealer would then give the customer a card that was supposed to correspond to the offer price. In this setting, the dealer could certainly give the buyer a card worth less than the offer price, but this rarely happened. The card received by the buyer was close in value to the price offered. Next, List went to the trading floor at the show and again recruited customers. But this time the customers approached dealers at their booth. The dealers did not know they were being watched. The scenario went something like this: as the customer approached the dealer’s booth, he would say, “Please give me the best Derek Jeter card you can for $20.” In this scenario, the dealers consistently ripped off the customers by giving them cards worth much less than the offer price. In fact, the dealers who were the worst offenders were the same dealers who refused to participate in List’s study. Do you believe that individuals who volunteer for experiments are scientific dogooders? That is, do you believe that in designed experiments subjects strive to meet the expectations of the researcher? In addition, do you believe that results of experiments may suffer because many experiments require individuals to volunteer, and individuals who are not do-gooders do not volunteer for studies? Now, explain why control groups are needed in designed experiments and the role they can play in neutralizing the impact of scientific do-gooders.

Obtaining a Simple Random Sample Based on the Military Standard 105E (ANS1/ASQC Z1.4, ISO 2859) Tables, a lot of 91 to 150 items with an acceptable quality level (AQL) of 1% and a normal inspection plan would require a sample of size 13 to be inspected for defects. If the sample contains no defects, the entire lot is accepted. Otherwise, the entire lot is rejected. A shipment of 100 night-vision goggles is received and must be inspected. Discuss the procedure you would follow to obtain a simple random sample of 13 goggles to inspect.

What is the role of randomization in a designed experiment? If you were conducting a completely randomized design with three treatments and 90 experimental units, describe how you would randomly assign the experimental units to the treatments

Problem 31RE Tooth-Whitening Gum Smoking and drinking coffee have a tendency to stain teeth. In an effort to determine the ability of chewing gum to remove stains on teeth, researchers conducted an experiment in which 64 bovine incisors (teeth) were stained with natural pigments such as coffee for 10 days. Each tooth was randomly assigned to one of four treatments: gum A, gum B, gum C, or saliva. Each tooth group was placed into a device that simulated a huma chewing gum. The temperature of the device was maintained at body temperature and the tooth was in the device for 20 minutes. The process was repeated six times (for a total of 120 minutes of chewing). The researcher conducting the experiment did not know which treatment was being applied to each experimental unit. Upon removing a tooth from the chewing apparatus, the color change was measured using a spectrophotometer. The percentage of stain removed by each treatment after 120 minutes is given in the table. The researchers concluded that gums A and B removed significantly more stain than gum C or saliva. In addition, gum C removed significantly more stain than saliva. Source: Michael Moore et al. “In Vitro Tooth Whitening Effect of Two Medicated Chewing Gums Compared to a Whitening Gum and Saliva,” BioMed Central Oral Health 8:23, 2008 (a) Identify the research objective. ________________ (b) Is this an observational study or designed experiment? Why? ________________ (c) If observational, what type of observational study is this? If an experiment, what type of experimental design is this? ________________ (d) What is the response variable? ________________ (e) What is the explanatory variable? Is it qualitative or quantitative? ________________ (f ) Identify the experimental units. ________________ (g) State a factor that could affect the value of the response variable that is fixed at a set level. ________________ (h) What is the conclusion of the study?

Problem 32RE Reaction Time Researchers wanted to assess the effect ofm low alcohol consumption on reaction time in seniors. Their belief was that even low levels of alcohol consumption can impair the ability to walk, thereby increasing the likelihood of falling. They identified 13 healthy seniors who were not heavy consumers of alcohol. The experiment took place in late afternoon. Each subject was instructed to have a light lunch (such as a sandwich) and not to drink any caffeinated drinks in the 4 hours prior to arriving at the lab. The seniors were asked to walk on a treadmill on which an obstacle would appear randomly. The reaction time was measured by determining the time it took the senior to lift his or her foot upon the appearance of the obstacle. First, each senior walked the treadmill by consuming a drink consisting of water mixed with orange juice with the scent and taste of vodka. The senior was then asked to walk on the treadmill. The senior was then asked to drink two additional drinks (40% vodka mixed with orange juice). The goal was to have the senior reach a blood alcohol concentration around 0.05%. The senior then walked on the treadmill again. The average response time increased by 19 milliseconds after the alcohol treatment. The researchers concluded that response times are significantly delayed even for low levels of alcohol consumption. Source: Judith Hegeman et al. “Even Low Alcohol Concentrations Affect Obstacle Avoidance Reactions in Healthy Senior Individuals,” BMC Research Notes 3:243, 2010 (a) What type of experimental design is this? ________________ (b) What is the response variable in this experiment? Is it quantitative or qualitative? ________________ (c) What is the treatment? ________________ (d) What factors were controlled and set at a fixed level in this experiment? ________________ (e) Can you think of any factors that may affect reaction to alcohol that were not controlled? ________________ (f ) Why do you think the researchers used a drink that had the scent and taste of vodka to serve as the treatment for a baseline measure? ________________ (g) What was the conclusion of the study? To whom does this conclusion apply?

Multiple Choice A common tip for taking multiple-choice tests is to always pick (b) or (c) if you are unsure. The idea is that instructors tend to feel the answer is more hidden if it is surrounded by distractor answers. An astute statistics instructor is aware of this and decides to use a table of random digits to select which choice will be the correct answer. If each question has five choices, use Table I in Appendix A or a random-number generator to determine the correct answers for a 20-question multiple-choice exam.

Humor in Advertising A marketing research firm wants to know whether information presented in a commercial is better recalled when presented using humor or serious ary by adults between 18 and 35 years of age. They will use an exam that asks questions of 50 subjects about information presented in the ad. The response variable will be percentage of information recalled. Create a completely randomized design to answer the question. Be sure to include a diagram to illustrate your design.

Describe what is meant by a matched-pairs design. Contrast this experimental design with a completely randomized design.

Internet Search Go to an online science magazine such as Science Daily(www.sciencedaily.com) or an open-source online medical journal such as BioMed Central (www.biomedcentral.com) and identify an article that includes statistical research. (a) Was the study you selected a designed experiment or an observational study? (b) What was the research objective? (c) What was the response variable in the study? (d) Summarize the conclusions of the study.

Cell Phones Many newspaper articles discuss the dangers of teens texting while driving. Suppose you are a journalist and want to chime in on the discussion. However, you want your article to be more compelling, so you decide to conduct an experiment with one hundred 16- to 19-year-old volunteers. Design an experiment that will assess the dangers of texting while driving. Decide on the type of experiment (completely randomized, matched-pair, or other), a response variable, the explanatory variables, and any controls that will be imposed. Also, explain how you are going to obtain the data without potentially harming your subjects. Write an article that presents the experiment to your readers so that they know what to anticipate in your follow-up article. Remember, your article is for the general public, so be sure to clearly explain the various facets of your experiment.