How to do psychological research

Null hypothesis (H₀): A statement asserting no effect or relationship exists between variables.

Alternative hypothesis (H₁): A statement suggesting an effect or relationship exists between variables.

Falsifiable: Capable of being proven false through evidence or experimentation.

One-tailed/directional hypothesis: Predicts the direction of the effect or relationship between variables.

Two-tailed/non-directional hypothesis: Predicts an effect or relationship without specifying its direction.

Scientific theory: A well-supported explanation of phenomena based on evidence and observation.

Qualitative: Non-numeric data focusing on descriptions, themes, or patterns.

Quantitative: Numeric data emphasizing measurement and statistical analysis.

Experimental design: A method for testing hypotheses by manipulating variables to observe outcomes.

Observational design: A method of studying behavior without direct intervention or manipulation.

Experiment vs. Study: An experiment manipulates variables to test causation, while a study may simply observe relationships.

Cause-and-effect relationship: A connection where one variable directly influences another.

Independent variable (IV): The variable manipulated to assess its effect on the dependent variable.

Levels/conditions: The different values or categories of the independent variable.

Dependent variable (DV): The variable measured to determine the effect of the independent variable.

Control variable: A variable held constant to prevent it from influencing results.

Measured variable: A variable that is observed and recorded without manipulation.

Within-subjects/repeated measures: Design where the same participants are exposed to all conditions.

Between-subjects/independent design: Design where different participants are exposed to different conditions.

Variability: The extent to which data points differ from each other or the mean.

N: The sample size, or the number of participants in a study.

Counterbalancing: A method to control for order effects by varying the sequence of conditions.

Order effects: Changes in participants’ behavior due to the order of conditions.

Experimenter bias: Unintentional influence of the experimenter on results.

Participant bias: Participants’ behavior changes due to their awareness of being studied.

Hawthorne effect: Improved performance due to participants knowing they are observed.

Experimental group: The group exposed to the independent variable.

Control group: The group not exposed to the independent variable, serving as a baseline.

Placebo effect: A change in behavior due to participants’ expectations, not the treatment.

Single-blind: Participants are unaware of the condition they are in.

Double-blind: Both participants and researchers are unaware of the assigned conditions.

Confounds/extraneous variables: Variables other than the IV that may influence the DV.

Correlation: A statistical measure of the relationship between two variables.

Positive correlation: Both variables increase or decrease together.

Negative correlation: One variable increases as the other decreases.

Sample: A subset of individuals from the population being studied.

Population: The entire group of interest in a study.

Representative sample: A sample reflecting the characteristics of the population.

Random sampling: Selecting participants so each individual has an equal chance of inclusion.

Randomly assigned: Allocating participants to conditions by chance.

Convenience/opportunity sampling: Selecting participants based on availability or accessibility.

Reliability: The consistency of a measurement or test.

Validity: The extent to which a test measures what it claims to measure.