Designing Psychological Investigations

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  • Created by: Katie
  • Created on: 03-03-11 22:46

Research Methods and Concepts


- Involve an IV and a DV. All other variables are controlled so any changes to the DV are due to the IV NOT extraneous variables.

  • Laboratory Experiment (controlled environment, high internal validity because extraneous variables can be controlled. However some things may reduce internal validity, e.g. investigator/experimenter effects and demand characteristics. Control also increases replicability. Reduced external validity because less like everyday life.)
  • Field Experiment (natural experiment, more difficult to control extraneous variables than in a lab experiment. Experimenter effects reduced because participants are not aware of being in a study. Demand characteristics may still be present.)
  • Natural Experiment (experiment makes use of existing IV, e.g. treatment used for SZ patients. Cannot manipulate IV so causal conclusions cannot be made. Participants are not randomly allocated so may reduce validity. This may be the only way to study certain behaviours or experiences.)

Experimental Design: in any experiment there are several levels of the IV. Experimenters chose whether each participant are tested on all IV's (repeated measures) or thereare seperate groups for each IV (independent groups), or matched pairs where the participants in each independent group can be matched with participants in the other group using key variables such as age and IQ.

Self-Report Methods

Questionnaires and Interviews (finding out what people think and feel). Can have an unstructured interview, where questioned asked are based on previous answers by the interviewee. Structured questionnaires/interviews are more easily repeated.

May involve open questions where you can provide your own answer (rich insight but more difficult to analyse than closed questions.)

Problem with self-report measures: honesty, e.g. social desirability bias.

Observational Studies

- To watch what people do. Use behavioural categories to record particular instances of behaviour, also sampling methods such as recording behaviour every 30 seconds (time sampling) or every time a certain behaviour occurs (event sampling). May have observer bias.

Correlation Analysis

- Concerned with the relationship between 2 variables. These studies use a correlation analysis: doesn't establish causal relationship, but can identify relationships. Can be used with large data sets and easily replicated.

Case Studies

- Detailed study of an individual, institution or event. Most are longitudinal: follow an individual or group over an extended period of time. Difficult to generalise.

Other research methods: Content Analysis, Cross-cultural Research, Meta-analysis.


Issues of Reliability, Validity and Sampling


- How much we can depend on any particular measurement.

  • Experimental Research: in regards to an experiment, reliability refers to its replication (obtain the same result after repeating.)
  • Observational Techniques: observations should be consistent; 2 or more observers should produce the same record. Inter-rater or inter-observer reliability, the extent to which observers agree. Total agreements/total number of observations. 0.80 is good inter-rater reliability.
  • Self-report Techniques: Internal Reliability (is a measure of the extent to which something is consistent within itself), External Reliability (is a measure of consistency over several occasions.


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