Research Methods
Experiments
Experimental method:
Aims
- Purpose of the investigation
Hypotheses
- Testable operationalised statement.
Directional or non-directional
- Identifying a difference/ correlation or not. Choice depends on previous theory/ research.
Variables:
IVs and DVs
- IV manipulated, DV measured.
Levels of the IV
- Experimental and control conditions.
Operationalisation
- Defining variables so they can be measured.
Research issues:
Extraneous variables
- Nuisance variables but randomly distributed.
Confounding variables
- Vary systematically with IV
Demand characteristics
- Participants second guess their aims, alter their behaviour.
Investigator effects
- Influence of researchers on DV/design decisions.
Randomisation
- Chance methods to reduce researcher’s bias.
Standardisation
- Ensuring all participants have the same experience.
Experimental designs:
Independent groups
- Participants in each condition of experiment are different.
Repeated measures
- All participants take part in all conditions.
Matched pairs
- Similar participants paired on participant variables, allocated to condition A or B.
, Evaluation:
Independent groups
- Participants variables not controlled (use random allocation).
- Less economical. No order effects.
Repeated measures
- Order effects (use counterbalancing). Demand characteristics. Participant variables controlled.
More economical.
Matched pairs
- No order effects. Cannot match participants exactly. Time-consuming.
Types of experiment:
Lab experiments
- IV is manipulated in a controlled setting. Participants go to research.
Field experiments
- IV is manipulated in a natural setting. Researchers go to participants.
Natural experiments
- IV changes naturally. DV/setting may be natural or in a lab.
Quasi experiments
- IV based on existing differences between people, the effect on DV is recorded.
Evaluation:
Lab experiments
- High internal validity (control CVs/EVs, causes and effects shown), replication more possible
(support for findings). However low external validity (generalisability, mundane realism), low
internal validity (demand characteristics).
Field experiments
- Higher external validity (more authentic, realism). Lower interna; ca;idity (less control). Ethical
issues (consent not possible).
Natural experiments
- Only option for practical/ethical reasons, high external validity (real-world problems). Limited
opportunities, no random allocation (CVs), low realism in a lab, no manipulation of IV (can’t claim
cause and effect).
Quasi experiment
- If in the lab, issues as for lab experiments. No random allocation, no manipulation of IV (can’t
claim cause and effect).
Sampling
Population and sample:
Random sample
- Equal chance of selection, lottery
Systematic sample
- Selecting every nth person from the list.
Stratified sample
Experiments
Experimental method:
Aims
- Purpose of the investigation
Hypotheses
- Testable operationalised statement.
Directional or non-directional
- Identifying a difference/ correlation or not. Choice depends on previous theory/ research.
Variables:
IVs and DVs
- IV manipulated, DV measured.
Levels of the IV
- Experimental and control conditions.
Operationalisation
- Defining variables so they can be measured.
Research issues:
Extraneous variables
- Nuisance variables but randomly distributed.
Confounding variables
- Vary systematically with IV
Demand characteristics
- Participants second guess their aims, alter their behaviour.
Investigator effects
- Influence of researchers on DV/design decisions.
Randomisation
- Chance methods to reduce researcher’s bias.
Standardisation
- Ensuring all participants have the same experience.
Experimental designs:
Independent groups
- Participants in each condition of experiment are different.
Repeated measures
- All participants take part in all conditions.
Matched pairs
- Similar participants paired on participant variables, allocated to condition A or B.
, Evaluation:
Independent groups
- Participants variables not controlled (use random allocation).
- Less economical. No order effects.
Repeated measures
- Order effects (use counterbalancing). Demand characteristics. Participant variables controlled.
More economical.
Matched pairs
- No order effects. Cannot match participants exactly. Time-consuming.
Types of experiment:
Lab experiments
- IV is manipulated in a controlled setting. Participants go to research.
Field experiments
- IV is manipulated in a natural setting. Researchers go to participants.
Natural experiments
- IV changes naturally. DV/setting may be natural or in a lab.
Quasi experiments
- IV based on existing differences between people, the effect on DV is recorded.
Evaluation:
Lab experiments
- High internal validity (control CVs/EVs, causes and effects shown), replication more possible
(support for findings). However low external validity (generalisability, mundane realism), low
internal validity (demand characteristics).
Field experiments
- Higher external validity (more authentic, realism). Lower interna; ca;idity (less control). Ethical
issues (consent not possible).
Natural experiments
- Only option for practical/ethical reasons, high external validity (real-world problems). Limited
opportunities, no random allocation (CVs), low realism in a lab, no manipulation of IV (can’t claim
cause and effect).
Quasi experiment
- If in the lab, issues as for lab experiments. No random allocation, no manipulation of IV (can’t
claim cause and effect).
Sampling
Population and sample:
Random sample
- Equal chance of selection, lottery
Systematic sample
- Selecting every nth person from the list.
Stratified sample
