INTR STATISTCL REASONING
INTR STATISTCL REASONING STAT 110
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This 25 page Class Notes was uploaded by Shane Marks on Monday October 26, 2015. The Class Notes belongs to STAT 110 at University of South Carolina - Columbia taught by L. Hendrix in Fall. Since its upload, it has received 42 views. For similar materials see /class/229650/stat-110-university-of-south-carolina-columbia in Statistics at University of South Carolina - Columbia.
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Date Created: 10/26/15
Chapter 1 Where do data come from STAT 110 7 Introduction to Descriptive Statistics Scope of Applications Last month s unemployment rate in SC was 118 up from 69 1 year earlier 70 of people aged 18 to 24 believe that downloading music off the Internet is no different from buying a used CD or recording music borrowed from a friend as opposed to 36 of people 65 or older Low income children who received high quality day care did better on academic tests given years later and were more likely to go to college and hold good jobs than other similar children STAT 110 7 Introduction to Descriptive Statistics Scope of Applications In a reliability study tribologists aim to determine the main cause of failure in a jet engine assembly Recently failures reported in the field have had an effect on customer confidence for safety concerns In a marketing project store managers in Aiken SC want to know which brand of coffee is most liked among the 1824 year old population STAT 110 7 Introduction to Descriptive Statistics Scope of Applications In a clinical trial physicians on a Drug and Safety Monitoring Board want to determine which of two drugs is more effective for treating HIV in the early stages of the disease In a paint production process a chemical reaction may produce a change in color depending on the temperature and stirring rate in the vessel where the reaction takes place An engineer would like to understand how the color is affected by the temperature and stirring rate STAT 110 7 Introduction to Descriptive Statistics Scope of Applications The Human Relations Department at a major corporation wants to determine employee opinions about a prospective pension plan adjustment In a public health study conducted in Sweden researchers want to know whether or not smoking i causes lung cancer andor ii is strongly linked to a particular social class STAT 110 7 Introduction to Descriptive Statistics Scope of Applications Shaquille O39Neill claims that he can make free throws when they count Is there any evidence to support his claim Which professions boast the highest salaries for undergraduates An advisor at USC is interested in collecting information which she can provide to her advisees A physical therapist is trying to determine which type of therapy conventional vs experimental is better at helping his patients recover from serious wrist injuries STAT 110 7 Introduction to Descriptive Statistics Individuals and Data Statistics is the science or art of data Individuals are the objects described by a set of data Individuals may be people but they may also be animals or things A variable is any characteristic of an individual A variable can take different values for different individuals The actual measurements recorded for individuals are called data STAT 110 7 Introduction to Descriptive Statistics Example 1 Name Major Points Grade Advani Sura Comm 397 B Barton David Hist 323 C Brown Annette Lit 446 A Chiu Sun Psyc 405 B Cortez Maria Psyc 461 A Individuals Variables STAT 110 7 Introduction to Descriptive Statistics Example 2 Make and Model Vehicle Type Transmission Cylinders City Highway MPG MPG BMW 325C Subcompact Automatic 6 19 27 BMW 325C Subcompact Manual 6 20 29 Buick Regal Midsize Automatic 6 20 30 Chevy Blazer SUV 2WD Automatic 6 16 21 Individuals Variables STAT 110 7 Introduction to Descriptive Statistics Example 3 In an agricultural study in Kansas researchers want to know which of three 7 fertilizer compounds produces the Ind39V39duaIS highest wheat yield in kgplot An experimenter uses 15 plots of land Each fertilizer is applied to 5 plots of land After harvest the resulting yield is measured Variable Fertilizer 1 Fertilizer 2 Fertilizer 3 648 565 658 605 538 732 634 594 595 482 611 663 555 588 702 STAT 110 7 Introduction to Descriptive Statistics 3 Ways to gather Data 1 Observational Study 2 Sample Survey 3 Experiment STAT 110 7 Introduction to Descriptive Statistics 1 Observational Study An observational study observes individuals and measures variables of interest but does not attempt to influence the responses A response variable is a variable that measures an outcome or result of a study The purpose of an observational study is to describe some group or situation STAT 110 7 Introduction to Descriptive Statistics Definitions The population for a statistical study is the entire group of individuals about which we want information A sample is the part of the population from which we actually collect information and is used to draw conclusions about the whole STAT 110 7 Introduction to Descriptive Statistics 13 2 Sample Survey A Sample survey is a type of observational study that surveys a group of individuals by studying only some of its members selected because they represent the larger group of individuals It is a survey because the individuals provide their own responses It is a sample survey because the individuals participating in the survey are a sample of the population STAT 110 7 Introduction to Descriptive Statistics Census A census is a sample survey that attempts to include the entire population as the sample It is estimated that the 2000 census missed 012 of the American population The US Census is required by the constitution every 10 years the 2010 census is underway I STAT 110 7 Introduction to Descriptive Statistics 15 Example 4 The University of Pennsylvania s National Annenberg Election Survey conducted a poll from July 30 to August 5 2004 They asked Do you favor or oppose Federal funding of research on diseases like Alzheimer s using stem cells taken from human embryos The survey reported that the poll consisted of 1345 randomly selected adults in the United States Population Sample I STAT 110 7 Introduction to Descriptive Statistics 16 Example 5 The American Community Survey ACS contacts 3 million households including some in every county in the US This new Census Bureau survey asks each household questions about their housing economic and social status Population Sample STAT 110 7 Introduction to Descriptive Statistics Example 6 Video adapter cables have pins that plug into slots in a computer monitor The cable will not work if pins are bent or broken A store chooses 5 cables from each lot and inspects the pins If any of the cables have bent or broken pins the entire lot is sent back Population Sample STAT 110 7 Introduction to Descriptive Statistics 18 Example 7 A sociologist wants to know the opinions of employed adult women about government funding for day care She obtains a list of the 580 members of a women s club and mails a questionnaire to 100 of these women selected at random Only 41 questionnaires are returned Population Sample What percentage of the women contacted responded STAT 110 7 Introduction to Descriptive Statistics 19 3 Experiment An experiment deliberately imposes some treatment on individuals in order to observe their responses The purpose of an experiment is to study whether the treatment causes a change in the response Virtually all scientific research involves conducting welldesigned experiments Researchers hope the results from these experiments support a research hypothesis I STAT 110 7 Introduction to Descriptive Statistics 20 Example 8 Salmonella bacteria are widespread in human and animal populations and there are over 2000 known serotypes The reported incidence of salmonella illnesses in humans is about 17 cases per 100000 people A food scientist wants to see how withholding feed from pigs prior to slaughter can reduce the size of gastrointestinal tract lacerations during the actual slaughtering process This is an important issue since pigs infected with salmonella may contaminate the food supply through these lacerations among other routes including fecal matter and meat juices STAT 110 7 Introduction to Descriptive Statistics 21 Example 8 cont d Individuals pigs Population all marketbound pigs Sample 45 pigs from 3 farms 15 per farm assigned to three treatments Treatment 1 no food withheld prior to transport Treatment 2 food withheld 12 hours prior to transport Treatment 3 food withheld 24 hours prior to transport Data were measured on many variables body temperature prior to slaughter weight prior to slaughter treatment assignment the farm from which each pig originated number of lacerations recorded size of laceration cm STAT 110 7 Introduction to Descriptive Statistics 22 Example 8 cont d How should we assign pigs to one of the three treatments Why would one want to use animals from three farms Why might body temperature or prior weight be of interest STAT 110 7 Introduction to Descriptive Statistics 23 Example 9 Experiment Sample Survey or Observational Study Is your school s football team called for fewer penalties in home games than away games Do college students perform better on exams when Mozart is playing softly in the background than when no music is playing Are college students satisfied with the quality of education they are receiving STAT 110 7 Introduction to Descriptive Statistics 24 Statistical conclusions hold on average for groups of individuals They don t tell us much about one individual STAT 110 7 Introduction to Descriptive Statistics 25
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