#6 Step 6: Within-Group Design

Question 1

What is within-group experimental design?

Answer 1

Uses a single group of participants and tests/observes each individual in all the different treatment conditions being compared

Question 2

Advantages of within-group design?

Answer 2

Considered the ultimate equivalent groups because the existing differences are equal

Variability due to individual differences is not damaging because participants are being compared to themselves

Question 3

Disadvantages of within-group design?

Answer 3

Time-related confounds because it could threaten internal validity

Question 4

History

Answer 4

Any environmental events other than the treatment that can change over time and may affect the scores in one treatment

Question 5

Maturation

Answer 5

Any systematic changes in physiology and psychology that can occur during a research study and affect the score

Question 6

Instrumentation

Answer 6

Changes in measurement overtime

• experimenter’s mood
• especially for research studies that span over a long period of time

Question 7

Regression towards the mean

Answer 7

The tendency for extreme scores on any measurement to move towards the mean when the measurement procedure is repeated
- closely tied to the reliability of the measurement

Question 8

Order Effect

Answer 8

Occurs when the experience of being tested in one treatment has an influence on the participant’s scores in a later treatment condition

• Practice Effect
• Fatigue Effect
• Contrast Effect

Question 9

Solutions to Time-Related Confounding Variables

Answer 9

1. Controlling time
2. Switch to a between-subject design (best strategy whenever a researcher has reason to expect substantial order effects)
3. Counterbalancing: changing the order in which treatment conditions are administered from one participant to another so that the treatment conditions are matched with respect to time