Research in Psychology

• Research begins with a clear research question
• Hypotheses are specific predictions derived from theory
• Psychological constructs must be operationalised into measurable variables
• Study design determines what conclusions can be drawn
• Data are collected from a sample and analysed statistically
• Conclusions evaluate hypothesis support and study limitations

Goals of Psychological Research

• Describe behaviour by identifying patterns
• Predict behaviour using relationships between variables
• Explain behaviour by identifying underlying mechanisms
• Control behaviour by applying interventions to produce change

Characteristics of Science

• Objective measurement to reduce bias
• Empirical evidence guides conclusions
• Methods must be replicable and verifiable
• Findings are public and subject to peer review

Research Design

• Research design is chosen based on the research question
• Different designs allow different conclusions
• Timing-based designs
  • Cross-sectional compares groups at one point in time
  • Longitudinal tracks change over time
• Control-based designs
  • Experimental designs involve manipulation and control
  • Non-experimental designs observe naturally occurring variables
• Data source designs
  • Self-report uses questionnaires
  • Behavioural or observational data measure actions directly

Causality vs Association

• Correlation does not imply causation
• Three criteria for causal conclusions
  • Covariance between variables
  • Temporal precedence of cause before effect
  • Internal validity through control of alternative explanations
• Non-experimental designs cannot rule out all alternative causes
• Spurious correlations occur when variables appear related due to a third factor

Populations and Samples

Term	Definition
Population	The full group of interest
Sample	A subset of the population
Data	Measurements collected from the sample

Data and Variables

• Unit of observation refers to what is being sampled
• Data are recorded observations stored in a dataset
• Variables are characteristics that differ across observations
• Quantitative variables are numeric
• Qualitative variables are categorical

Types of Data

Type	Description
Quantitative	Numeric values
Qualitative	Categorical or descriptive values

Type of Quantitative Data	Description
Discrete	Separate, countable values
Continuous	Any value within a range

Levels of Measurement

Level	Key Features
Nominal	Unordered categories
Ordinal	Ordered categories
Interval	Equal spacing, no true zero
Ratio	Equal spacing with a true zero

Independent and Dependent Variables

• Independent variable is used to explain or predict outcomes
• Dependent variable is the outcome being measured
• Experimental designs allow causal interpretation
• Non-experimental designs allow prediction but not causation

Extraneous and Confounding Variables

• Extraneous variables are additional variables not of primary interest
• Confounding variables provide alternative explanations
• Confounds reduce internal validity
• Experimental control helps reduce confounding

Experimental Control

• Control allows exclusion of alternative explanations
• Random allocation improves internal validity
• Only experimental designs can fully establish causality

Role of Statistics in Research

• Psychological research focuses on large groups
• Individuals vary widely in behaviour and experience
• Measuring entire populations is impossible
• Statistics summarise data and identify patterns
• Inferential statistics estimate population effects from samples

Inferential Statistics

• Used to generalise findings beyond the sample
• Based on probability
• Estimate likelihood that observed effects reflect population effects
• Replace repeated population-level testing

Quantitative Research Methods

• Use numerical data to test hypotheses
• Allow aggregation and comparison
• Support objective, evidence-based conclusions