Experimental Designs

Question 1

What is independent groups?

Answer 1

1. PPs are divided equally into _ amount of groups
2. Group 1 participates in Condition 1, Group 2 in Condition 2, etc
3. Each PP only participates in one condition of experiement

Question 2

What are the strengths of independent groups?

Answer 2

• As PPs only partake in one ondition, PPs performance on later tasks will not be impaired due to boredom/fatigue. Therefore we can be certain that changes in the DV are due to IV manipulation. As results are not impacted by order effects, validity increases
• Demand characteristics are less likely. As PPs take part in only one condition, they are less likely to realise the aim. This means there are less demand characteristics as PPs have little opportunity to figure out the aims and so won’t change behaviour to suit or refute them. This they are less likely to display unnatural behaviour, increasing validity

Question 3

What are the weaknesses of independent groups?

Answer 3

• There are individual differences (PP variation) that may affect results. This is because 2 different groups of PPs are being compared and so one group may perform better at the task due to their individual characteristics e.g. IQ. Therefore, we can’t be certain that any changes in the DV are due to IV manipulation as existing differences between PPs may have affected the DV. Thus decreasing the validity of the findings and conclusions drawn
• It is very time consuming as researcher needs to find double the amount of PPs compared to repeated measures. This decreases practicality/utility

Question 4

What is repeated measures?

Answer 4

1. All PPs are put into one group
2. Same group completes ALL conditions of experiments

Question 5

What are the strengths of repeated measures?

Answer 5

As the same PPs take part in all conditions of the experiments there are no individual differences thus we can be confident that any changes in DV are due tp IV manipulation rather than existing differences between PPs. This increases the validity of findings and conclusions.

Question 6

What are the weaknesses of repeated measures?

Answer 6

• There are order effects, this is when PPs perform worse in later conditions due to boredom/fatigue. Therefore, we can no longer be certain that changes in the DV are due to IV manipulation. As results are impaxted by order effects, validity decreases
• There may be demand characteristics. As PPs take part in all conditions they may realise the aims of the experiment. This could lead to demand characteristics as PPs may change their behaviour to suit/refute the aim thus displaying unnatural behaviour and so decreasing validity

Question 7

What is matched pairs design?

Answer 7

1. PPs are tested on a trait e.g. IQ
2. PPs who have similar scores in this test are paired up
3. One PP from each pair is allocated to Condition 1,the second PP to Condition 2
4. Each PP only partakes in one condition of the experiment

Question 8

What are the strengths of matched pairs design?

Answer 8

• No order effects. This is when PPs perform worse in the later condition due to boredom/fatigue. Therefore, we can be sure that changes in the DV are only due to IV msnipulation and so can be certain of a cause and effect relationship
• Demand characteristics are less likely. As PPs take part in only one condition, they are less likely to realise the aim. This means there are less demand characteristics as PPs have little opportunity to figure out the aims and so won’t change behaviour to suit or refute them. This they are less likely to display unnatural behaviour, increasing validity
• There will be LESS individual differences than independant groups as PPs are matched based on the trait that is most likely to impact behaviour in the experiment

Question 9

What is the weakness of matched pairs design?

Answer 9

Matching PPs can be costly and time consuming. This is because additional tasks are required to be able to pre-test PPs trait and then find an even match among all the other PPs