[R] help in interpreting paired t-test

[peter dalgaard]

On Sep 21, 2011, at 18:39 , Marc Schwartz wrote:

> Jeremy,
> 
> Correlation alone is irrelevant when comparing two separate sets of measurements on the same specimen. Correlation does not mean good agreement, but good agreement tends to infer high correlation.

Marc,

I think Jeremy is well aware of that. He just said that the power to detect a (small) difference is higher when the correlation is higher. (Since V(X-Y) = 2*(1-rho)*sigma^2 if X and Y have the same variance sigma^2)

-- 
Peter Dalgaard, Professor
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com