Experimental Designs Flashcards
what is an experimental design?
the different ways in which pp’s can be organised in relation to the experimental conditions
what happens in an independent groups design?
two separate groups experience two different conditions. The results are compared
evaluate the independent groups design
Order effects aren’t an issue and pp’s are less likely to guess the aim and wont get bored so behaviour will be more natural. This will control CV’s. However it requires more pp’s, time and money. Pp’s in the different groups aren’t the same in terms of participant variables. This may reduce the validity
what is the matched pairs design?
pp’s are paired together on variables relevant to the experiment. One ppt from each pair is allocated to one condition and the other to another
Evaluate matched pairs design
Order effects and demand characteristics are less of a problem. Ppt’s are matched on a variable that is relevant to the experiment. Increases the validity
However pp’s can never be exactly matched and matching them may be time consuming so not all ppt variables can be addressed. Twice as many ppts are needed which is time consuming and expensive
What is the repeated measures design?
All pp’s experience both conditions and the mean scores are compared
Evaluate repeated measures design
Participant variables are controlled therefore there is a higher validity. Fewer pp’s are needed therefore less time is spent recruiting them.
However, each ppt has to do at least 2 tasks + the order of them may be significant. Order effects may arise due to boredom from repeating tasks. Alternatively, ppt performance may improve due to practice. Demand characteristics are an issue.
What is random allocation?
Random allocation attempts to evenly distribute pp’s across the conditions by randomly allocating them to the conditions (eg from a hat) and tries to address the problem of ppt variables in an independent groups design
What is counterbalancing?
Counterbalancing is an attempt to control order effects in a repeated measures design. In counterbalancing, half the pp’s take part in condition A then B, and the other half do B then A.
Eg: ppt 1: A-B ppt 2: B-A ppt 3: A-B and so on
What is a pilot study?
Small scale trial run of an investigation to test procedures so that research design can be modified.
What is a single blind study?
A ppt doesn’t know the aims of the study so demand characteristics are reduced
What is a double blind study?
Both ppt and researcher don’t know the aims of the study to reduce demand characteristics and investigator effects
