The study relied on the researchers' observations, which could have introduced bias into the findings.

Experiments: Laboratory, field, natural

Self-reports: Questionnaires, interviews

Case Studies

Observation: Overt/covert, participant/non-participant, structured/unstructured, naturalistic/controlled

Correlations

Hypotheses and Aims

Variables: Independent, dependent, operationalization

Experimental Design: Independent measures, matched pairs, repeated measures, counterbalancing, random allocation, order effects

Controlling of Variables: Extraneous, uncontrolled, participant, and situational variables, standardization

Types of Data: Quantitative and qualitative

Sampling of Participants: Sample, population, opportunity sampling, random sampling, volunteer sampling