Experimental Designs

Question 1

What is an independent groups design?

Answer 1

Ppts take part in one condition only. Each condition has a different group of ppts. (AO1)

Question 2

How is independent groups conducted?

Answer 2

Recruit a group of ppts → split into equal groups → each group allocated to one condition. (AO1)

Question 3

Strength of independent groups (order effects)?

Answer 3

No order effects as ppts only do one condition (no boredom, fatigue, practice). (AO3)

Question 4

Strength of independent groups (when useful)?

Answer 4

Can be used when repeated measures isn’t suitable, e.g. comparing genders in quasi experiments. (AO3)

Question 5

Limitation of independent groups (individual differences)?

Answer 5

Differences between groups may affect DV (e.g. memory ability) → ↓ internal validity. (AO3)

Question 6

Control for independent groups problem?

Answer 6

Use random allocation so ppts have equal chance of being in any condition → reduces group differences. (Control)

Question 7

What is a repeated measures design?

Answer 7

All ppts take part in all conditions. (AO1)

Question 8

How is repeated measures conducted?

Answer 8

Ppts complete one condition → after time gap, complete the other condition → tasks matched for difficulty. (AO1)

Question 9

Strength of repeated measures (individual differences)?

Answer 9

Removes individual differences as same ppts used in all conditions → ↑ internal validity. (AO3)

Question 10

Strength of repeated measures (sample size)?

Answer 10

Fewer ppts needed as same group used in all conditions. (AO3)

Question 11

Limitation of repeated measures (order effects)?

Answer 11

Order effects may occur (boredom, fatigue, practice, lasting effects) → ↓ internal validity. (AO3)

Question 12

Limitation of repeated measures (demand characteristics)?

Answer 12

Ppts may guess aim as they do all conditions → may change behaviour → ↓ internal validity. (AO3)

Question 13

Control for repeated measures problem?

Answer 13

Use counterbalancing (ABBA method): half do A→B, half do B→A → balances order effects. (Control)

Question 14

What is a matched pairs design?

Answer 14

Ppts are matched on important variables (e.g. IQ, age), then one from each pair is allocated to each condition. (AO1)

Question 15

How is matched pairs conducted?

Answer 15

Choose variable → pre-test ppts → match pairs → randomly allocate each to one condition. (AO1)

Question 16

Strength of matched pairs (individual differences)?

Answer 16

Matching reduces effect of individual differences → changes in DV more likely due to IV. (AO3)

Question 17

Strength of matched pairs (order effects)?

Answer 17

No order effects as ppts only do one condition. (AO3)

Question 18

Limitation of matched pairs (time consuming)?

Answer 18

Matching ppts is very time consuming, especially with pre-tests. (AO3)

Question 19

Limitation of matched pairs (still differences)?

Answer 19

Can’t match on every variable → individual differences still possible → ↓ validity. (AO3)

Question 20

Limitation of matched pairs (large sample)?

Answer 20

Needs a large pool of ppts to find suitable matches. (AO3)