Experimental Designs

Question 1

How many conditions do ppts take part in in an independent groups?

Answer 1

One condition. Each condition has a different group of ppts

Question 2

How many conditions do ppts take part in in a repeated measures?

Answer 2

All conditions.

Question 3

What are ppts matched on in matched pairs?

Answer 3

Important characteristics in the study e.g. IQ or age. Each ppt is given an appropriate test matching two ppts on with the same score. Each pair is randomly allocated across each condition.

Question 4

How is independent measures conducted? (3 steps)

Answer 4

A group of ppts are recruited
They are split into equal sized groups
A different group is allocated each condition.

Question 5

How is repeated measures conducted. (3 steps)

Answer 5

Ppts complete one condition
After significant time lapse (an hour) they compete other condition
The task (DV) should be different but matched on difficulty/ measuring the same thing

Question 6

How is matched pairs conducted? (4 steps)

Answer 6

Choose a variable to match ppts on
Test ppt on variable before the study
Match ppts with the same scores
Randomly allocate each member of pair to one condition

Question 7

STRENGTH: Why is there no order effects in independent measures? What is this unlike?

Answer 7

Ppts only take part in one condition so they will not get bored, fatigued, better, or have lasting effects from one condition to the next. UNLIKE repeated measures where ppts take part in all conditions so there could be order effects.

Question 8

STRENGTH: Why can independent measures be used when repeated measure is not appropriate? Give an example.

Answer 8

E.g. quasi experiment looking at gender differences as each condition needs different ppts

Question 9

WEAKNESS: Why may individual differences affect the DV in independent measures? What is this unlike?

Answer 9

There are separate groups of ppts in each condition e.g. some may have better memory which wouldn’t be suitable in memory study (CONTEXT) lowering internal validity. UNLIKE repeated measures where the same ppts are used in both conditions to reduce the effect of individual differences.

Question 10

STRENGTH: Why are individual differences between each ppt removed in repeated measures? Give example. What is this unlike?

Answer 10

E.g. IQ as potential confounding variables, the same ppts take part in all conditions (CONTEXT). Therefore, the researcher can be more sure that changes in the DV are due to the IV and not any other variables. Increasing the internal validity UNLIKE Independent group measures that Will use different participants in different conditions so individual differences could affect the dependent variable.

Question 11

STRENGTH: Why does repeated measures require fewer ppts?

Answer 11

The same participants take part in all conditions (context). Unlike in an independent measures design as separate groups are needed for separate conditions.

Question 12

WEAKNESS: Why my order effects occur in repeated measures?

Answer 12

Participants take part in more than one condition, they may perform worse in the second condition (due to boredom or fatigue) or better in the second condition (due to practice), or there may be lasting effects from condition a to condition b (context) lowering the internal validity. Unlike independent measures where participants only take part in one condition, so cannot be susceptible to order affects.

Question 13

WEAKNESS : Why is there increased chances of demand characteristics in repeated measures?

Answer 13

Participants take part in all conditions. They may pick up on clues given off by the researcher as they spend much more time with them, or from the research situation, and change their natural behaviour to help or hinder the research (context) lowering the internal validity. Unlike independent groups where participants are less likely to pick up on clues as they only take part in one condition of the research

Question 14

STRENGTH: Why does matched pairs reduce individual differences between participants?

Answer 14

Participants are matched on variable is important to the research E.G.IQ/age/happiness. (Context). Therefore, the researcher can be more sure any changes in the dependent variable are due to the independent variable not any other variable. Unlike in an independent measures were separate participants are in separate conditions.

Question 15

STRENGTH: Why will there be no order affects in matched pairs?

Answer 15

Participants only take part in one condition so they will not get bored/fatigued or better at the task/have lasting effects from one condition to the next (context). Unlike repeated measures were participants take part in all conditions and could have order affects.

Question 16

WEAKNESS: Why is matched pairs time-consuming?

Answer 16

Participants have to be matched up and similar participants have to be found (context) especially if a pre test is needed to much participants on a certain characteristic. Psychologist will need a very large pool of people. Unlike repeated measures design we use the same participants in all conditions.

Question 17

WEAKNESS: Why can’t individual differences be fully eliminated in matched pairs?

Answer 17

Participants and marched on variable is important for the research but not able to match participants on all variables (context). Therefore this question validity of matched pairs design. Unlike repeated measures were each condition will use the same participants therefore individual differences will be fully eliminated.