Experimental Methods

What is a quasi-experiment?

Can take place in the field or under laboratory conditions. The experimenter does not manipulate the IV.

What are 2 strengths of the repeated measures design?

+ Individual differences are not a confounding variable + Fewer participants need to be recruited

What are 2 strengths of the matched pairs design?

+ No order effects + Individual differences are reduced

What are 2 strengths of the independent groups design?

+ No order effects + Task variables controlled (e.g. you can use the same word list twice in a recall experiment)

What are 3 overall weaknesses of the experimental method?

- Lack ecological validity - Lack construct validity - Demand characteristics are likely to occur

What is 1 weakness of the repeated measures design?

- Order effects are likely to occur

What is 1 weakness of the independent groups design?

- Participant variables may influence the DV (this is less likely if you use a larger sample, though)

What are the features of a laboratory experiment?

- Random allocation of participants (no experimenter bias) - Control over situational variables - IV can be manipulated

What is 1 weakness of the matched pairs design?

- Time consuming and expensive

What is order effect? Give 3 examples of order effects.

Behaviour is effected because participants take part in two or more conditions in a particular order. E.g. fatigue effect, practice effect, demand characteristics.

Describe an example of a field experiment.

Having someone in uniform or not in uniform (IV) order someone to pick up litter on the street. DV is wether it is picked up.

What is 1 strength of laboratory experiments?

High validity because of control over extraneous variables; change in the DV is likely to result from change in the IV.

What does counterbalancing do to reduce the impact of order effects?

The order in which conditions are encountered is balanced across all participants. This means that every possible combination of order of conditions occurs the same number of times.

How does randomisation control extraneous variables?

The order or use of variables is decided by chance so there is no experimenter bias.

What happens in the repeated measures design?

The same participants are used in each condition.

What is 'experimental design'?

The way participants are used in conditions within the experiment.

What is 1 strength of field experiments?

They allow some control over extraneous variables.

What is 1 weakness of field experiments?

They offer no control over environmental factors.

What are 3 overall strengths of the experimental method?

+ High level of control over extraneous variables so cause and effect can be established + Empirical value + Objective because they aren't easily influenced by experimenter bias

What is an extraneous variable?

A variable besides the IV which could affect the DV.

What is a confounding variable?

A variable besides the IV which may have affected the DV.

Describe the matched pairs design.

Different participants are used in each condition, but they are matched according to key characteristics.

Describe the independent groups design.

Different participants are used in each condition. There are no attempts to match participants across conditions.

What are the 3 types of experiment?

Field experiments, laboratory experiments and quasi-experiments.

What is 1 weakness of laboratory experiments?

Lack ecological validity.

What are the 3 types of design?

Matched pairs, repeated measures, independent groups.

Give 1 strength of quasi- experiments.

More ethical because participants are not being manipulated. These could be used to study drug addiction.

Give 1 weakness of field experiments.

No control over environmental factors.

Name the 3 ways of controlling extraneous variables.

Standardisation, counterbalancing and randomisation.

Explain what is meant by the experimental method.

The IV is manipulated to affect the DV, the DV is then measured. It is the process which is important, not how data is collected.

What happens in field experiments?

The experiment takes place in a natural setting and the IV is still controlled by the experimenter.