2.2.6 Experimental design

Question 1

what is Independant Groups Design

Answer 1

IGD is where participants are in separate (independant) groups
- each group does one levlel of the IV

e.g group A does hte task with the TV on (one level of IV) group B does the task with the TV off (other level of IV)

we compare the performance (DV) of the two groups

Question 2

what is a Disadvantage of using IDG

Answer 2

• researcher cannot control the effects of participant variables (e.g the different abilities or characteristics of each participant)

e.g ptps form group A migth happen to have better memories than than group B (acts as a confounding variable)

• independant groups design needs more participants than repeated measures design in order to end up with the same amount of data

Question 3

how do we deal with the disadvantages of using IDG

Answer 3

• randomly allocate participants to conditions which theoretically distribute participant variables evenly
• random allocation can be done by putting the participants names in a hat and drawing out the names so that every other person goes in Group A

Question 4

what is Repeated Measures Design?

Answer 4

• All participants receive all levels of the IV

e.g each participant does the task with the TV on, e,g does a memory test
then a week later, does a similar test with the TV off

we compare the performance (DV) of the ptps on the two tests

Question 5

what are the Disadvantages of RMD

Answer 5

• the order of the conditions may affect performance (an order effect)
  e.g participants may do better on the second test becuase of a practise effect or because they are less anxious
  > in some situations, people may do worse on the second test due to boredom (boredom effect)
• when ptps do the second test they may guess the purpose of the experiment, which may affect their behaviour
  e.g some ptps may purposefully do worse on the second test because they want it to appeaer as if they work less well in the afternoon

Question 6

how do we deal with the disadvantages of RMD

Answer 6

• researchers may use two different tests to reduce a practise effect
  > though the two tests must be equivialnt
  > this can be done by contructing a test of 40 items and randomly allocating items to Test A and Test B
• the main way order effects are dealt with are using counterbalancing (ensures each condition is tested first or second in equal amounts)
• in order to avoid ptps guessing aim of study, a cover story can be presented about the purpose of the test

Question 7

what is Matched Pairs Design?

Answer 7

• the use of two groups of ptps but match ptps on key characteristics beleived to affect perfromance on the DV (IQ or time spent watching TV)

> one member of pair is allocated to group A, the other to group B
procedure is the same as for independant groups

• characteristics for matching must be relevant to the study
  e.g you wouldnt match ptps on gender when testing memory unless evidence proved women had better memories

Question 8

what are the Disadvantages of MPD

Answer 8

• time consuming
• difficult to match ptps on key characterisitcs
• researcher would have to start with a large group of ptps to match pairs well
• not possible to control all ptp variables
  > can only match relevant variables but others could be important
  e.g in a memory exp. you might match on memory abilities but later find out some ptps were involved in a teaching programme to boost memory skills and you should have matched on this

Question 9

how do we deal with the Disadvantages of MPD

Answer 9

• restrict number of variables to match on to make it easier
• conduct a pilot study to consider key variables that might be important when matching