Psychology 242 Research Methods II Dr David Allbritton
Psychology 242 Research Methods II Dr. David Allbritton http: //www. depaul. edu/~dallbrit
Introduction and Review • Syllabus and Course Requirements • Types of research: Experimental vs. Nonexperimental • Review of Basic Statistics • Review of Validity and Control
Types of Research • Non-experimental Methods (“correlational”) – – Observational research Archival research Case studies Survey research • Experiments – IV & DV – Maximizes internal validity (shows causation) • Quasi-Experiments
Statistics • Sample: Descriptive Statistics • Population: Inferential Statistics
Descriptive Statistics • Measures of central tendency – Mean – Median – Mode • Measures of variability – Standard deviation (SD) – Variance (SD squared) • Correlation – measure of relatedness
Distributions • Histograms • Density Curves • Normal Distributions – Symmetrical around the mean – Mean = median = mode – Standard Deviation and area under the curve: 68: 95: 99. 7 rule – Example: IQ mean = 100, SD = 15
Populations and Samples • Population: all the possible scores – All living humans – All voters • Sample: a subset of the population – Random sample – best kind; unbiased • Relationship of sample mean to population mean - example
Validity & Control • Validity – is the research sound? • Threats to Validity – e. g. , confounds • Control – removing threats to validity
Validity of Research • Internal Validity • Does the IV (and not some other factor) really cause the changes in the DV? • Ruling out other causes (confounds) • Construct Validity • Does the study support theory it is supposed to and no other theories? • Ruling out other theories (alternative explanations) • External Validity • Do the results generalize to other people? • Statistical Validity • Does the IV cause the changes in the DV, or could they be due to chance?
Strategies for Control in Experiments • • • Subject as Own Control (within-subjects) Random Assignment Counterbalancing Building in Nuisance Variables Replication
- Slides: 10