SW 983 - REPEATED MEASURES DESIGNS
Repeated measures involves the measurement of the same subjects at different points in time.
It is the natural design to use when the concern is with performance trends over time. The
simplest example of a repeated measures design is dependent samples t test where the same
subjects are pretested and posttested on a dependent variable with an intervening treatment.
Note that this is a design that requires special statistical treatment.
Advantages:

Control for individual differences (i.e. reduce error variance)

More economical (requires fewer subjects)

Study of trends across time (time series, pannel studies).
Problems:

Carry-over effects

Practice effects

Fatigue

Sensitization

Statistical (correlated errors, i.e. observations are not independent)
Analysis:

Can think of repeated measures as special case of MANOVA where each
observation time period is treated as a separate dependent variable.

SPSS still has a MANOVA module, however, it appears that they are replacing it
with GLM through pull down menu (Analyze – GLM – Repeated Measures.