Module 13: Correlated-Groups and Developmental Designs

Question 1

Correlated-groups design

Answer 1

the participants in the experimental and control groups are related.

Question 2

Within-participants design (repeated-measures designs)

Answer 2

A type of correlated-groups design in which the same participants are used in each condition. Random sample is required, random assignment not because everyone will participate in both groups.

Pro:

• fewer participants
• less time
• increase statistical power

Con:

• confounds (testing effects)
• Demand characteristics

Question 3

Variability due to individual differences

Answer 3

differences in performance when multiple groups are used, because they are not the same. The difference must be from the independent variable.

Question 4

Testing effects (or order effects)

Answer 4

Practice and fatigue effects

Question 5

Counterbalancing

Answer 5

Practice and fatigue effects can be equalized by counterbalancing, systematically varying the order of conditions for participants. So, half would participate in the control condition first, and the other half would participate in the experimental condition first.

Complete counterbalancing: is the one described above.

Partial counterbalancing: is to randomize the order of presentation of conditions for each participant, or randomly select the number of orders that matches the number of participants (since you can’t do all types of order)

Question 6

Latin square

Answer 6

A counterbalancing technique to control for order effects without using all possible orders

Question 7

Carryover effect

Answer 7

participants carry something with them from one condition to another (for example with drug testing).

Question 8

Matched-participants experimental designs

Answer 8

conditions on variable(s) that the researcher believes is (are) relevant to the study. You attempt to achieve as much equivalence between groups as possible.

Pro:

• Testing effects and demand characteristics are minimized
• Groups more equal
• Participants are matched on variables important to the study

Con:

• More participants needed
• Mortality (if one participant drops out, the other needs to as well)
• The matching itself is a weakness, because finding a individual who wants to participate who is equal to another willing individual is difficult. Especially, when there are multiple variables the researcher is looking for (e.g. height and weight).

Question 9

Developmental designs

Answer 9

use age as a variable, 3 types:

• Cross-sectional design
• Longitudinal design
• Sequential design

Question 10

Cross-sectional designs

Answer 10

researchers study individuals of different ages at the same time.
• Pro: wide variety of ages can be studied in a short period.
• Con: cohort effect

Question 11

Cohort effect

Answer 11

is a generational effect in a study that occurs when the eras in which individuals are born affect how they respond in the study

Question 12

Longitudinal design

Answer 12

the same participants are studied over a period of time.
• Pro: Eliminates cohort effects.
• Con:
- more expensive and time-consuming
- Attrition problems over time because those who drop out of the study likely differ in some possibly meaningful way from those who remain. For instance, those who drop out may be healthier, wealthier, or more conscientious, and in general they may have more stable lives.

Question 13

Sequential design

Answer 13

The sequential design is a combined cross-sectional and longitudinal design in that a researcher begins with participants of different ages (cross-sectional design). Later, the researcher retests the same individuals (longitudinal design).
• Pro: allows researchers to examine cohort effects, usually without taking as much time as a longitudinal design alone.
• Con: more expensive and time-consuming