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Chapter 5 Textbook Notes

by: Courtney Santasero

Chapter 5 Textbook Notes PSY 250

Marketplace > University at Buffalo > Psychlogy > PSY 250 > Chapter 5 Textbook Notes
Courtney Santasero
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Introduction to Research Methods in Psychology
Dr. Lacy
Class Notes
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This 7 page Class Notes was uploaded by Courtney Santasero on Thursday October 1, 2015. The Class Notes belongs to PSY 250 at University at Buffalo taught by Dr. Lacy in Summer 2015. Since its upload, it has received 49 views. For similar materials see Introduction to Research Methods in Psychology in Psychlogy at University at Buffalo.


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Date Created: 10/01/15
Chapter 5: Introduction to Experimental Research ● Robert Sessions Woodworth’s Colombia bible.  ● An experiment is a systematic research study in which the investigator  directly varies some factor holds all other factors constant, and observes the  results of the variation.  ○ Independent variables are under the control of the experimenter. ○ Extraneous variables are factors being held constant. ○ Dependent variables are the behaviors measured.  ● The independent variable is the factor of interest to the experimenter, the one being studied to see if it will influence behavior. ○ Manipulated independent variables. ● Manipulated Independent Variables ○ Have a minimum of two levels (involves a comparison between at  least two things). ○ Ex. marijuana comparison, two doses. ● Field experiments are experiments that take place in the field.  ● Manipulated independent variables tend to fall into three overlapping categories: ○ Situational ○ Task ○ Instructional ● Situational variables are features in the environment that participants might  encounter.  ● Task variables are different tasks that participants are asked to perform.  ● Instructional variables are manipulated by telling different groups to perform a particular task in different ways.  ● In an experimental group, the treatment is present. ● In a control group, the treatment is withheld.  ● Control groups only occur in research when it is important to have a baseline. ● Damisch et al. study on luck. ● Researcher tries to control extraneous variables, variables that are not of  interest to the researcher but that might influence the behavior being studied if  not controlled.  ○ If a researcher fails to control extraneous variables , they can  systematically influence the behavior being measured, and the result is called  confounding. ○ A confound is any uncontrolled extraneous variable that  covaries with the independent variable and could provide an alternative  explanation of the results.  ● The term dependent variable is used to describe those behaviors that are the  measured outcomes of experiments.  ● Two major problems that occur with poorly chosen variables: ceiling and floor  effect. ○ A ceiling effect occurs when the average scores for the group  are so high that no difference can be determined between conditions.  ○ A floor effect occurs when all the scores are extremely low,  usually because the task is too difficult for everyone.  ● Subject variables are existing characteristics of the individuals participating  in the study. ● Ji et al.’s vertical rod study on culture and gender. ● Studies using independent variables that are subject variables are occasionally  called ex post facto studies, natural group studies, or quasi experiments.  ● Causal conclusions about the causes of behavior cannot be drawn from  experiments using subject variables.  ● Four types of validity are statistical conclusion validity, construct validity, external  validity, and internal validity. ● Statistical conclusion validity concerns the extent to which the researcher  uses statistics properly and draws the appropriate conclusions from the statistical analysis.  ○ The data might be measured wrong. ○ The researcher might selectively report some analyses that came  out as predicted but might not report on others. ○ Reliability of the measures used.  ● In experimental research, construct validity refers to the adequacy of the  operational definitions for both the independent and the dependent variables in a  study.  ● External validity is the degree to which a research finding can be generalized beyond the specific context of the experiment being conducted.  ○ Results should generalize in three ways: ■ To other populations. ■ To other environments. ■ To other times.  ○ A subject pool refers to a group of students, typically those in  introductory psychology courses, who are asked to participate in research as part of a course requirement.  ○ Kohlberg’s six­stage theory on moral development has been  criticized due to its lack of external validity. ■ Kohlberg only sampled males in his study.  ● Ecological validity is research with relevance for the everyday cognitive  activities of people trying to adapt to their environments.  ● Internal validity is the degree to which an experiment is methodologically  sound and confound­free.  ● To judge whether change has occurred, one procedure is to evaluate prior to an  experience with a pretest and then after the experience with a posttest.  ○ Using a control group is very important so that history and  maturation can be ruled out as causes for the change.  ● Regression to the mean: If a score on a test is extremely high or low, a  second score taken will be closer to the mean score. Can be a threat to the  internal validity of a study if a pretest score is extreme and the posttest score  changes in the direction of the mean.  ● Testing is considered a threat to internal validity when the mere fact of taking a  pretest has an effect on posttest scores.  ● Instrumentation is a problem when the measurement instrument changes from  pretest to posttest.  ○ Often a problem with observation, those doing the observing might be better with practice making the pretest instrument different from the posttest  instrument.  ● If groups in different conditions are not equal, subject selection effects may  occur.  ● Attrition occurs when participants fail to complete a study, usually but not  necessarily a longitudinal study; those finishing the study may not be equivalent  to those who started it.  Chapter 6: Methodological Control in Experimental Research ● A between­subjects design is an experimental design in which different  groups of participants serve in the different conditions of the study. ○ Used if the independent variable is a subject variable.  ■ Unless behaviors occurring at two different ages  are being compared, and the same persons are studied at two different  times in their lives.  ■ Unless the marital status is a subject variable and  the same people are studied before and after a marriage or divorce.  ○ Prime advantage: each subject enters naive with respect to the  hypothesis being tested.  ○ Disadvantages: ■ Large numbers of people necessary. ■ Differences between conditions may be due to  group differences.  ● Creating equivalent groups is  important here.  ● Creating Equivalent Groups: ○ Simple random assignment. ○ Matching procedure followed by random assignment. ● Random assignment is a method of placing participants, once selected for a  study, into the different groups. Every person has an equal chance of being  placed in any of the groups being formed.  ○ A researcher can use blocked random assignment, a procedure  which ensures that each condition of the study has a participant randomly  assigned to it before any condition is repeated a second time.  ○ Most oftenly associated with laboratory research.  ● In matching, participants are grouped together on some subject variable  such as their characteristic level of anxiety and then distributed randomly to the  different groups in the experiment.  ○ Ex. in the memory study, the matching variable would be  anxiety. ○ Two important conditions must be met: ■ You must have good reason to believe the  matching variable will have a predictable effect on the outcome of the  study.  ■ There must be a reasonable way of measuring or  identifying participants on the matching variable.  ● A within­subjects (repeated measures) design is an experimental design in  which the same participants serve in each of the conditions of the study. ○ Might be necessary during studies that are shorter, it might make  more sense to give participants a sequence of short tasks to follow rather than to  have a new group for each section of the sequence. ○ Might be necessary when volunteers are scarce because the  entire population of interest in small.  ○ They eliminate the equivalent group problems.  ○ One major problem: order effect, which is that once a participant  has completed the first part of a study, the experience or altered  circumstances could influence performance in later parts of the study.  ■ Progressive effects assumes that performance  changes steadily from trial to trial.  ■ A carryover effect occurs when sequences  produce effects different from those of other sequences.  ○ Counterbalancing is any procedure designed to control for  sequence effects.  ○ Complete counterbalancing involves using every possible  sequence at least once.  ○ Partial counterbalancing (incomplete counterbalancing) is used  when a subset of the total numbers is used.  ○ A Latin square is a form of partial counterbalancing in which  each condition of the study occurs equally often in each sequential  position and each condition precedes and follows each other condition  exactly once.  ● Testing More than Once Per Condition ○ In reverse counterbalancing, the experimenter presents the  conditions in one order first and then again in reverse order.  ○ In block randomization, the basic rule is that every condition  must occur once before any condition can be repeated.  ● In a cross­sectional study, design makes ages the independent variable and  DIFFERENT groups of people are tested, each group is of a different age.  ○ Ex. a cross­sectional study comparing the language performance  of 3­, 4­, and 5­year­old children would use THREE groups of children.  ○ Between­subjects ○ Pro: can be done in a shorter period of time.  ○ Con: cohort effect­ a cohort is a group of people born at the  same time; cohort effects can reduce the internal validity of cross­sectional studies because differences between groups could result from the effects  of growing up in different historical areas.  ● In a longitudinal study, design makes age the independent variable and the  SAME group of people is tested repeatedly at different ages.  ○ Ex. the same language performance study testing the same group of children at the ages of 3, 4, and 5.  ○ Within­subjects ○ Pro: no cohort effect. ○ Con: time and attrition.  ● In a cohort­sequential design, a group of subjects is selected and retested  every few years and also retested over time.  ○ Design would look like the following: Year of the Study Cohort # 2010 2015 2020 2025 2030 2035 2040 1 55 60 65 2 55 60 65 3 55 60 65 4 55 60 65 5 55 60 55 ● Seattle Longitudinal Study (K. Warner Schaie, 2005) ○ Begun in 1956, it was designed to examine age­related changes  in various mental abilities.  ● Biases falls into two broad categories: ○ Those affecting the experimenter.  ○ Those affecting participants. ● Experimenter bias­ occurs when an experimenter’s expectations about a  study affect its outcome.  ○ Experimenters can influence outcomes in ways other than their  expectations. The experimenter’s race, gender, demeanor, friendliness, and  overall attitude can also affect participants’ behavior.  ● To avoid experimenter bias, there are protocols­ detailed descriptions of the  sequence of events in a research session; used by an experimenter to ensure  uniformity of treatment of research participants.  ○ In a double blind procedure, neither the participant nor the  person conducting the experimental session know which condition of the  study is being tested; often used in studies evaluating drug effects.  ■ In a single blind procedure, subjects are left in the dark but experimenters know the condition in which each subject is  being tested.  ● Subject bias can occur when the behavior of the subjects is influenced by  their beliefs about how they are supposed to behave in a study.  ○ The Hawthorne Effect occurs when participant behavior is  influenced by the mere knowledge of being in an experiment and therefore  important to the experimenter.  ○ The good subject role occurs when the participants try to guess  about the researcher’s hypothesis and act in ways that will confirm it.  ■ Demand characteristics are a feature of the  experimental design or procedure that increases the chances that  participants will detect the true purpose of the study.  ○ Evaluation apprehension is a form of anxiety experienced by  participants that leads them to behave so as to be evaluated positively by  the experimenter.  ○ The primary method for controlling subject bias is to reduce  demand characteristics to the minimum, possibly through deception or use of a  placebo control group. ■ This can also be done with a manipulation check  which can be accomplished during debriefing by asking participants in a  deception study what they believe the true hypothesis to be.  ■ Can also be done through field research where  participants are unaware of their participation in a study.


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