TEST: experiments, sampling methods, sampling bias

quantitative research

• objectively collects + analyses numerical data to describe/predict/control variables

• goal → test causal relationships between variables. predict + generalise results to larger population

• operates w/ variables (= characteristic objectively quantified)

• researchers aim to establish general laws of behaviour across diff. contexts

• research ultimately support/rejects the theory being tested

hypotheses

• researchers first read thru research available on their RQ (= literature review)

• after aim → hypothesis (prediction of how IV affects DV)

  • experimental hypothesis predicts causal relationship between IV DV (want to support)

  • null hypothesis states IV has no effect on DV (want to reject)

  • clearly state IV DV + operationalise (clearly define how it will be manipulated/measured)

• experimental and control group

• psych. research never proves → supports experimental or fails to reject null hypothesis

experiment — key characteristics

• quantitative research method. yields quantitative data (allows for stats)

• goal → determine whether causal relation between variables exists (simplest has 1 IV, 1 DV)

• findings → context-bound (few applications irl)

• variables must be operationalised (expressed in terms of observable behaviour)

true experiment

• aim → establish causality between IV and DV. 

• Ps randomly assigned to conditions

• other variables controlled to establish causality

• standardised procedure to allow replication + ensure reliability

• often use deception to avoid demand characteristics

• independent samples/repeated measures design

• often have high internal validity (setting may lower external validity)

4 types of experiments

4 types of variables

participants in research

• people taking part = participants

• psychologists define target population (group of interest for study)

• sample → Ps chosen from target population

  • sample should be representative of population (may lack population validity otherwise)

  • bigger = better

sampling techniques and sampling bias

1. opportunity → Ps selected based on naturally occurring groups

2. random → each member of target population has equal chance of being selected

3. self-selected → Ps volunteer (based on ad/internet)

4. snowball → Ps recruit other Ps for study

5. stratified → sample matches makeup of population. Ps from various subgroups randomly selected

Sampling Bias → when non random sampling technique used (P variables in sample may not be representative and may influence outcome)

• psych is WEIRD (western, educated, industrialised, rich, democratic)