Exercise: ANCOVA for baseline/follow-up
measurements
Shoulder pain and acupuncture
Reanalyze the original data
Re-estimate the ANCOVA model for the Kleinhenz et al. (1999)data
Run a power simulation for a replication study
Draw plausible pre-CMS values
Specify the minimum relevant average treatment effect (ATE)
Set the remaining parameters to plausible values
What is the sample size required for the test to detect the effect
with 80% power?
How robust is the power simulation when you repeat it with a new set
of pre-CMS values? Try it!
Recover the parameters of the ANCOVA model
Reference
Kleinhenz, J., K. Streitberger, J. Windeler, A. Güßbacher, G. Mavridis,
and E. Martin. 1999. “Randomised Clinical Trial Comparing the
Effects of Acupuncture and a Newly Designed Placebo Needle in Rotator
Cuff Tendinitis.”Pain 83 (2): 235–41.