Within group designs 5.2

Question 1

Within groups advantages

Answer 1

•Participants serve as their own controls
•Less error variance
•More powerful statistical tests
•Less likely to make a Type II error
•Fewer ppts required (usually a relatively minor point)
•If it is not a problem, it is generally better to use a within- than a between-
design

Question 2

Within groups disadvantages

Answer 2

• Greater chance of demand characteristics
• Experiments take longer
• Greater potential for problems/confounds associated with time

Question 3

Within groups design

Answer 3

•Pretest-posttest measures
(Measure each ppt before and after a manipulation (or intervention).
•This is a within-groups measure
•Pretest-posttest measures are often used in between-groups designs)

•Repeated-measures design
(Measure each ppt multiple times in each condition
•One of the most common designs used in exp research

• Within-subjects design with a single observation per condition
• Less common
• Longitudinal design
• Measure a participant multiple times over a long period of time, often years

Question 4

Repeated measures designs

Answer 4

• Very common design type
• Within-subjects manipulation
• Record multiple observations/measurements in each condition
• Very important if you are using a DV that has a lot of error

Question 5

Longitudinal design

Answer 5

Measure the same participants on variables of interest at different
points in their lives.•A within-subjects measure/design for studying development
•An exception to the rule that subject variables (e.g., age) require between group designs

Question 6

Cross Sectional designs

Answer 6

•Between-groups counterpart to 
longitudinal designs on aging and 
development
•Non-equivalent groups
•Cohort effect confounds

Question 7

Longitudinal vs Cross section

Answer 7

• Both investigate ppts at different ages
• Both involve correlations between age and other variables
• Longitudinal
• Within subjects (same people at different ages)
• Data collection takes a long time (sometimes decades)
• Changes across the lifespan of individuals
• Covaries with cultural and technological changes (a confound)
• Cross-sectional
• Between subjects (different people at different ages)
• Suffer from cohort effect confounds
• Relatively fast data collection
• Snapshot of similarities and differences of people of different ages

Question 8

Pilot Studies

Answer 8

Pilot studies are short runs of your research conducted before your
actual study (like beta testing)
•You want to discover and fix any problems before you start running
the real experiment
•Participants and data in the pilot study are not counted in the
methods of the actual research