1. Controlled-Trial Designs
See Batterham and Hopkins, Sportscience 9, 33-39, 2005.
Choice determined by availability of subjects, reliability of dependent variable, and time to wash out treatment.
Time Series
Weakest design
Any change post treatment could be coincidental.
Analyze using within-subject modeling
Fit line or curve to each subject's baseline.
Extrapolate to the post-test.
Paired t of observed post minus predicted post.

2. Posts-only Controlled Trial
Least disturbance of subjects
But large sample size.
Analyze via unequal-variances unpaired t.
Can get estimate of individual responses as an SD, but not usefully for individuals.

3. Pre-post Controlled Trial (or fully-controlled trial)
Most common design.
Analyze difference of changes via unequal-variances unpaired t.
Pre-post Crossover
Best design if all subjects motivated to know effect of treatment on themselves.
Analyze change of changes via paired t.
washout

4. Posts-only Crossover
Least number of subjects and tests when reliability high.
But can get estimate of individual responses only if include a repeat of one of the treatments for each subject.
Analyze via paired t.
Important to control for the order effect, if it is substantial and there are unequal numbers in the crossover groups.
A spreadsheet is on its way.
washout

5. Decision Tree

6. Can you use a control group
or a separate control treatment? NO
YES
Time-series
trial
n=10-???

7. Can you do a pretest? NO
YES
Posts -
only
trial
n=2x 150

8. Will the intervention wash out in
an acceptable time for a crossover? NO
YES
Fully -
controlled
trial
n=2x -

9. washout+intervention period?
Is the measure
reliable b
over
washout+intervention
period? NO
YES
Are you limited
by subjects
or resources? NO
YES
Fully -
controlled
Simple
crossover
crossover
n=10-300
n=10-75