Research In Psychology: Methods & Design - Lecture Notes PDF

# RESEARCH IN PSYCHOLOGY: METHODS & DESIGN ## Eighth Edition ## Chapter 5. Introduction to Experimental Research ### Chapter Objectives * Describe the impact of Woodworth's 1938 Experimental Psychology on the way psychologists define an experiment * Define a manipulated independent variable and i...

# RESEARCH IN PSYCHOLOGY: METHODS & DESIGN ## Eighth Edition ## Chapter 5. Introduction to Experimental Research ### Chapter Objectives * Describe the impact of Woodworth's 1938 Experimental Psychology on the way psychologists define an experiment * Define a manipulated independent variable and identify examples that are situational, task, and instructional variables * Distinguish between experimental and control groups * Describe John Stuart Mill's rules of inductive logic and apply them to the concepts of experimental and control groups * Recognize the presence of confounding variables in an experiment and understand why confounding creates serious problems for interpreting the results of an experiment * Identify independent and dependent variables, given a brief description of any experiment * Distinguish between manipulated independent variables and those that are subject variables * Understand the interpretation problems that accompany the use of subject variables * Recognize the factors that can reduce the statistical conclusion validity of an experiment * Describe how construct validity applies to the design of an experiment * Distinguish between the internal and external validity of a study * Describe the various factors affecting an experiment's external validity * Describe and be able to recognize the various threats to an experiment's internal validity * Recognize that external validity might not be important for all research but that internal validity is essential * Understand the ethical guidelines for running a "subject pool" ### Essential Features of Experimental Research * Mill's inductive logic * Method of agreement * If X, then Y (sufficiency - X is sufficient for Y) * Method of difference * If not X, then not Y (necessity - X is necessary for Y) * Together - X is necessary & sufficient for producing Y * Agreement - analogous to experimental group * Difference - analogous to control group * Establishing independent variables (IVs) * Manipulated IVs * Situational * Task * Instructional * Experimental groups * given treatment (Research Example 6 - given a golf ball and told it was a "lucky" ball) * Control groups * treatment withheld (Research Example 6 - given a golf ball and not told it was a "lucky" ball) * Controlling extraneous variables * Confounds * Any uncontrolled extraneous variable * Results could be due to IV or to confound * Distributed practice example (Table 5.1) * Table 5.1. Confounding in a Hypothetical Distribution of Practice Experiment | | Monday | Tuesday | Wednesday | Thursday | Friday | |----------------|--------|---------|-----------|----------|---------| | Group 1 | 3 | - | - | - | Exam | | Group 2 | 3 | 3 | - | - | Exam | | Group 3 | 3 | 3 | 3 | - | Exam | Note: The 3s in each column equal the number of hours spent studying a chapter of a general psychology text. * Measuring dependent variables (DVs) * DVs are any behaviors measured in an experiment * Review scales of measurement (Ch. 4) * Problems * Ceiling effects - task is too easy, all scores very high, disguising any differences * Floor effects - task too difficult, all scores very low, disguising any differences * Solution * Task of moderate difficulty, determined through pilot testing ## Subject Variables * Subject Variables * Already-existing attributes of subjects in a study * Examples - gender, age, personality characteristic * Anxiety example * As a manipulated variable - induce different degrees of anxiety in participants * As a subject variable - choose participants who have different degrees of their typical anxiety * Research Example 7 * Subject variable #1 - culture (European Americans and East Asians); Subject variable #2 - gender (Women and men) * Research example * Greater field dependence for East Asians and for females (Figure 5.1) * Drawing conclusions when using subject variables * With a manipulated IV - Assuming no confounds, IV causes DV * With a subject variable * Groups may differ in several ways * IV cannot be said to cause DV * All that can be said - the groups differ from each other * Using both manipulated and subject IVs * Bandura's Bobo study (Box 5.2) * Manipulated - type of exposure to violence; Subject - gender ## The Validity of Experimental Research * Statistical conclusion validity * Proper statistical analyses and conclusions * Construct validity * Well-chosen and well-defined IVs and DVs * External validity * Internal validity ### External Validity * The extent to which research findings generalize to contexts other than those of the experiment ### Externally valid studies... 1. Generalize to other populations 2. Generalize to other environments (also, ecological validity) 3. Generalize to other times ### Internal Validity * Does my study actually answer the research question I proposed and designed to answer? ### Internally valid studies... 1. Have valid operational definitions 2. Have valid measurements 3. Have no confounds ## Threats to Internal Validity * Studies extending over time (pretests & posttests) * History * Maturation * Regression to the mean * Testing and instrumentation * Importance of using a control group * Participant problems * Subject selection - The Brady study - ulcers in executive monkeys * Attrition ## Creating Ethical Subject Pools * (Box 5.3) * Must be part of educational process for students * Should follow APA guidelines * Post requirement, describe it thoroughly * Provide reasonable alternative activities * Get IRB approval for all projects * Treat students well; provide mechanism for complaint * No penalties for no-shows * Follow all other aspects of the APA ethics code * Have a mechanism in place to assess the subject pool ## Summary * Experimental research involves independent and dependent variable, in an effort to test the effects of the IV on the DV. * We attempt to control for confounding variables to increase the internal validity of our study. * We must consider other possible threats to internal validity as they pertain to our study. * Once we identify IVs, DVs, and threats to validity, we design a study to control those threats. ## Chapter 6. Control Problems in Experimental Research ### Chapter Objectives * Distinguish between-subjects designs from within-subjects designs * Understand how random assignment can solve the equivalent groups problem in between-subjects designs * Understand when matched random assignment should be used when attempting to create equivalent groups * Understand when counterbalancing is needed to control for order effects in within-subjects designs * Distinguish between progressive and carry-over effects in within-subjects designs, and understand why counterbalancing normally works better with the former than with the latter * Describe the various forms of counterbalancing for situations in which participants are tested once per condition and more than once per condition * Describe the specific types of between- and within-subjects designs that occur in developmental psychology, and understand the problems associated with each * Describe how experimenter bias can occur and how it can be controlled * Describe how participant bias can occur and how it can be controlled ### Between-Subjects Designs * Different sets of subjects in each level of an IV * Comparison is between two different groups of subjects ### Necessary when... * Subjects in each condition have to be naïve (Example - Barbara Helm study) * Subject variable (e.g. gender) is the IV ### Main problem to solve - creating equivalent groups ### Creating Equivalent Groups * Random assignment * Each subject has equal chance of being assigned to any group in the study * Spreads potential confounds equally through all groups * Blocked random assignment - involves assigning a subject to each condition of the study before the condition is repeated * Matching * Deliberate control over a potential confound * Use when * Small n per group might foil random assignment * Some matching variable correlates with DV * Measuring the matching variable is feasible (Table 6.1) ### Within-Subjects Designs * Also called repeated-measures designs * Same subjects in every level of an IV * Comparison is within the same group of subjects - Used when comparisons within the same individual are essential (e.g., perception studies) * Eliminates the possibility that differences between levels of the IV could be due to individual differences ### Main problem to solve - order effects * Progressive effects * Carry-over effects (harder to control) * Performance on or experience in Sequence A-B may affect performance (i.e., "carry-over") on Sequence B-A ### Controlling Order Effects * Counterbalancing * Altering the order of the experimental conditions ### Testing once per condition * Complete counterbalancing (all possible orders = x!) * Test participants in every possible different order at least once * Works well with only a few conditions * Partial counterbalancing * Random sample of all possible combinations is selected * Latin square - every condition of the study occurs equally often in every sequential position, every condition precedes and follows every other condition exactly once ### Testing more than once per condition * Reverse counterbalancing * Example - A-B-C-D-D-C-B-A-A-B-C-D-D-C-B-A * Blocked randomization * Example - B-C-A-D-A-C-B-D-C-D-A-B-D-A-C-B * Research Example 8: When referees see red... ## Methodological Control in Developmental Research * Cross-sectional design * Between-subjects design * Potential for cohort effects - Worse with large age differences * Longitudinal design * Within-subjects design * Potential for attrition difficulties - But extremely low in Terman's famous longitudinal study of gifted children (Box 6.1) * Cohort sequential design * Combines cross-sectional and longitudinal ## Controlling for the Effects of Bias * Experimenter bias * Experimenter expectations can influence subject behavior * Clever Hans * Rosenthal studies * Controlling for experimenter bias * Automating the procedure * Using a double blind procedure (Research Example 9: Giving older adults caffeine in the afternoon...) * Participant bias * Hawthorne effect * Effect of knowing one is in a study * Misnamed perhaps (Box 6.2) - Importance of understanding history * "Good" subjects - Participants tend to be cooperative, to please the researcher * Evaluation apprehension - Participants tend to behave in ideal ways so as not to be evaluated negatively * Demand characteristics * Cues giving away true purpose and study's hypothesis (Research Example 10 - eating behavior...) ### Controlling for participant bias * Effective deception * Use of manipulation checks * Field research ## Ethical Responsibilities of participants * Box 6.3 * Be responsible * Show up for scheduled appointments, or inform research of cancellation * Be cooperative * Behave professionally when participating in research * Listen carefully * Ask questions if unsure of your rights or of what you are asked to do * Respect the researcher * Do not discuss study with others * Be actively involved in debriefing * Help the researcher understand your experience ## Summary * Between- and within-subjects designs are two types of experimental designs. * Methodological controls for between-subjects designs include random assignment and matching. * Methodological control for within-subjects designs include counterbalancing techniques and block randomization. * Developmental designs have unique control issues. * We should be mindful of experimenter and participant biases. * Methodological control is key to creating an internally valid study.