Research Methods - experimental designs

Question 1

What are experimental designs?

Answer 1

Refers to how ppts. are organised across conditions

Question 2

What is an independent groups design?

Answer 2

Ppts. only take part in 1 condition. Researchers randomly allocate group equally into 2 groups
1 group does condition 1 and the other does condition 2

Question 3

How are ppts. randomly allocated for independent groups design?

Answer 3

• Lottery method = obtaining list of all people in a sample, putting them in a hat and selecting a number of names for condition A (10) and for condition B (10)
• Random number generator = number every member of sample and use computer programme to get a random number and allocating half into each condition

Question 4

What is a repeated measures design?

Answer 4

All ppts. take part in both conditions. Ppts. either take part in condition 1 and then condition 2 or condition 2 and then condition 1

Question 5

What is a matched pairs design?

Answer 5

Ppts. only take part in 1 condition but are matched on a key characteristic with another ppt. One ppt. goes into one condition and the other ppt. goes into the other through random allocation

Question 6

What are order effects?

Answer 6

When ppts. take part in both conditions, they either get better (practice effects) or worse (fatigue effects) which affects the internal validity of the results

Question 7

What are strengths of independent groups?

Answer 7

• Order effects are reduced as ppts. only take part in1 condition
• Demand characteristics reduced as ppts. less likely to guess aim of the study

Question 8

What are weaknesses of independent groups?

Answer 8

• Ppt. extraneous variables between the groups which lowers internal validity
• Less economical as you need twice as many ppts.

Question 9

What are strengths of repeated measures?

Answer 9

• Ppt, extraneous variables are controlled for (reduced)
• Fewer ppts. needed (more economical)

Question 10

What are weaknesses of repeated measures?

Answer 10

• Order effects (ppts. could experience practice effects or fatigue effects which reduce the internal validity)
• Demand characteristics are more likely to occur as they pick up on cues better

Question 11

How could you reduce the order effects of repeated measures?

Answer 11

Counterbalancing - half the ppts. do condition A then B and half do condition B then A (also called ABBA technique)

Question 12

What are strengths of matched pairs?

Answer 12

• Ppts. only take part in 1 condition so order effects and demand characteristics are less of a problem
• Ppt. extraneous results are reduced

Question 13

What are weaknesses of matched pairs?

Answer 13

• Ppts. can never truly be matched
• Time consuming and expensive so less economical