Overview
This lecture covers key concepts and methods used in psychological research, including hypotheses, variables, sampling, experiment design, data handling, statistics, and ethics.
Hypotheses and Aims
- An aim is a clear statement outlining what the researcher plans to investigate and why.
- A hypothesis is a precise, testable statement predicting the relationship between variables.
- The null hypothesis (H0) states no difference or relationship exists.
- The alternate hypothesis (H1) suggests a difference or relationship exists.
- Hypotheses must operationalize variables—clearly defining how they are measured.
Types of Variables and Control
- Independent variable (IV): the one manipulated by the researcher.
- Dependent variable (DV): the one measured for change.
- Co-variables: variables measured in correlational studies.
- Extraneous variables: any variable other than the IV that can affect the DV.
- Demand characteristics and investigator effects can bias results.
- Control methods include random allocation, matched pairs, counterbalancing, standardized procedures, single/double-blind trials, and pilot studies.
Sampling Methods
- Target population: the group the study aims to generalize findings to.
- Random sampling: everyone has an equal chance; avoids bias but may be unrepresentative.
- Systematic sampling: select every nth person.
- Opportunity sampling: use whoever is available; quick but biased.
- Volunteer sampling: participants self-select in response to adverts.
- Stratified sampling: participants chosen to reflect subgroups in correct proportions.
Experimental Designs
- Independent groups: different participants in each condition; risk of participant variables.
- Repeated measures: same participants in all conditions; risk of order effects.
- Matched pairs: different groups matched on crucial variables; controls participant variables and order effects.
Types of Experiments & Self-Report
- Lab experiments: high control, low ecological validity.
- Field experiments: high realism, less control.
- Natural experiments: IV occurs naturally; high external validity, low control.
- Interviews and questionnaires use open (qualitative) and closed (quantitative) questions.
- Structured, semi-structured, and unstructured interviews differ in flexibility and required training.
Case Studies and Observational Methods
- Case studies gather in-depth data on individuals/groups using various methods.
- Controlled observations take place in lab settings; naturalistic in real environments.
- Overt observations: participants know they’re observed; covert: they don’t.
- Participant observation: researcher joins the group; non-participant: observes from outside.
- Use operationalized behavioral categories for reliable recording.
Correlation and Data Handling
- Correlational studies measure relationships; do not imply causation.
- Scattergrams display correlational data.
- Quantitative data: numerical, easy to analyze statistically.
- Qualitative data: descriptive, rich detail but subjective.
- Primary data is newly collected; secondary data is pre-existing.
Descriptive Statistics
- Measures of central tendency: mode (most frequent), median (middle value), mean (arithmetic average).
- Range measures spread of data.
- Bar charts show categorical data (bars don't touch); histograms show continuous data (bars touch).
- Normal distribution is symmetric, with mean, median, and mode at center.
Ethics in Research
- Key ethical considerations: informed consent, right to withdraw, protection from harm, confidentiality, debriefing.
- Alternatives for consent include prior general, retroactive, and presumptive consent.
- Ethics committees and cost-benefit analyses help balance participant welfare with research goals.
Key Terms & Definitions
- Operationalization — defining variables so they can be measured.
- Extraneous variable — any factor other than the IV that can affect the DV.
- Demand characteristics — cues that influence participant behavior.
- Random allocation — assigning participants to groups by chance.
- Counterbalancing — controlling order effects in repeated measures.
- Central tendency — statistical measures (mean, median, mode) representing "average."
- Ecological validity — the extent study findings generalize to real-life settings.
Action Items / Next Steps
- Review worksheet on research methods (if available from instructor).
- Practice calculating mean, median, mode, and range using sample data sets.
- Read ethical guidelines by the British Psychological Society (BPS).
- Prepare definitions and evaluations for each sampling and research method.