Sunday, August 21, 2005

A probability issue

If a country implements a family planning policy as below:

If the first child is a boy, no second child is allowed.
If the first child is a girl, a second child can be allowed and no third child is allowed.

Will the sex ratio (male/famale) still be 1?

Interim Analysis

In a recent meeting with some investigators, we discussed the protocol for a phase II clinical trial. When I ask whether or not if we need to consider the interim analysis, several investigators immediately oppose it citing that it will cost us the p-values. It seems that the investigators have been well informed the multiplicity and alpha-spending issue for the interim analysis or multiple look at the data.

I have a feeling that investigators seems to be afraid of the interim analysese because it may cost the power for the final analysis.