Psychology

• Random Sampling: A sample where every member of the population has an equal chance of being selected for the study.
• Sampling methods: Random, systematic, stratified, convenience, and random.
• Experimental Designs: Repeated Measures, Matched participants, Independent Groups.
• Repeated measures design: Participants are tested under both conditions (experiment and control).
• Matched pairs design: Each participant is matched with another to ensure similarity between groups.
• Placebo Effect: refers to the participants' behavior being influenced by their expectations of how they should behave, caused by the belief that they have received some treatment. Can be solved by the single-blind procedure.
• Single Blind Procedure: The researcher does not know which group the participant belongs to.
• Double blind procedure: Neither the researcher nor the participant knows who is receiving what condition.
• Random Allocation: Randomly assigning participants into either the experimental or control group using random numbers table.
• Experimenter Effect: The tendency for an experimenter to influence the behavior of participants. Can be eliminated by using the double-blind procedure.
• Types of Variables: Dependent, Independent, Extraneous, Confounding.
• Extraneous variables: Any factors other than the IV that may affect the DV
• Confounding variable: A factor that affects both the independent and dependent variables at the same time.
• Operationalized Variables: variables that have been defined and explained in terms of how they will be measured in an experiment. E.g 'aggression' can be operationally defined as 'how many times someone is hit with a sword'
• Types of Reliability: internal, parallel form, test-retest, inter-rater.
• Internal reliability: consistency between items on a scale or questionnaire.
• Test-Retest: Consistency over time.
• Inter-Rater: Consistency between different people rating the same behaviour/trait.
• Parallel Form: Consistency when using two versions of the same measure.
• Types of Validity: Context, Content, Internal, External.
• Context Validity: a form of internal validity that involves deciding whether the test can be used to support the theory that is being tested.
• Content Validity: Also known as Face Validity, a form of internal Validity that involves examining the instrument to decide whether it appears to be measuring what it is meant to.
• Internal Validity: A type of validity that refers to how well an instrument measures what it claims to measure. It includes content validity and construct validity.
• External Validity: The extent to which results from one sample or setting are generalisable to other samples or settings.
• Types of Inferential Tests: Paired and Unpaired T-tests, The Mann-Whitney U, Wilcoxon Signed-Rank.
• Paired t-test: Used when there are two scores per participant (e.g., pre-post).
• Unpaired t-test: Used when there is only one score per participant (e.g., group comparison).
• Mann-Whitney U Test: Nonparametric alternative to unpaired t-test; used with ordinal data. Is a test of the null hypothesis. Doesn't require normal distribution.
• Wilcoxon Signed Rank Test: Cannot be assumed to have normally distributed data. Used to compare 2 sets of scores from the same participants. Creates a Z value as well as the P value.
• Types of Errors: Type 1, Type 2.
• Type 1 Error: The outcome of the test will result in the null hypothesis being mistakenly rejected. **False Positive**
• Type 2 Error: The outcome of the test results in the null hypothesis not being rejected when it actually should be. **False Negative**