Jan 24: Assignment 2 Questions

My question relates more to the assignment than to the technical details: What is the level of statistical knowledge we should expect of the clients? This may have impact on how we explain things in the report.

DavidLee (talk)‎

1. ANCOVA. In order to suggest a suitable sample size for ANCOVA of the change in headache frequency we need to estimate the Variance of the error term, which can be estimated from the Sum of Squares Error (SSE) after the regression fitting. The paper does not provide paired data on each patient: How do we give a reasonable estimate?

2. ANCOVA. RE:Treatment effect used in power calc. One way to interpret the effect is the difference in migraine frequency between trt/ctrl groups Given the same baseline value: what is a reasonable size of scientific interest? If there is no way of getting this question answered by the time a consulting report is due, is it good enough to present sample sizes calculated under several scenarios? (perhaps show result graphically)

3. Change Scores Analysis. What is an effect size (difference in mean change) of scientific interest?

VivianMeng (talk)‎

1. On page 524, in "statistical analysis" section, is the 15% drop-out rate a generally assumed value in such type of trials, or is it based on result from previous acupuncture trials?

2. On page 524, in "associated symptoms" section, how is the Tukey test conducted?

GuohaiZhou (talk)‎