As Prof. Ripley said, the test on contrast is valid only if you selected the contrast before seeing the data. Using the same data for both hypothesis generation and hypothesis confirmation is extremely hazardous! Andy
From: Igor Roytberg [mailto:ir1982 at u.washington.edu] Hello, If you determine the means of x treatments and see that one is larger than the others, can you use a sample normal to determine how statistically significant the difference is? or would contrasts by a better tool? How would one go about to do this in R? Thanks for any help (since R is new to me), Igor