Chapter 6 Textbook Notes
Chapter 6 Textbook Notes PSY 250
Popular in Introduction to Research Methods in Psychology
Popular in Psychlogy
This 4 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 8 views. For similar materials see Introduction to Research Methods in Psychology in Psychlogy at University at Buffalo.
Reviews for Chapter 6 Textbook Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 10/01/15
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.