analysis plan: example
• The primary endpoint is free testosterone level, measured at
baseline and after the diet intervention (6 mo).
• We expect the distribution of free T levels to be skewed and will log-
transform the data for analysis. Values below the detectable limit for
the assay will be imputed with one-half the limit.
• The primary analysis will be a comparison of 6-mo changes in free T
between the two diet arms, using Student’s independent t-test with
two-sided p<0.05 as critical value.
• We will follow the intention-to-treat principle, analyzing each subject
as randomly assigned regardless of compliance with diet.
• In secondary analyses we will use multiple regression to adjust for
covariates including age, pubertal stage, insulin responsiveness.
• We will test for interactions, particularly for modification of the diet
effect on free T by pubertal stage and insulin responsiveness.