Hi, I have a question regarding two way anova. I have a data sheet as following: ID -- representing the same sample gets several repeated measures at the same time point group -- treated vs untreated time -- different time point (3, 9, 15 hours) signal -- measurement signal I use the aov function and formula = signal ~ (group*time) + Error (ID/(group*time) Questions: 1. is this the right way Error (ID/(group*time) to handle multiplicated repeated measures of the same sample (by ID) at the same time point? I have checked on the web and it looks like there is some controvercial discussion. Can you educate me here? 2. In the result of the model.tables (aov.study, "means"), the means value under "group:time" of treated and untreated vs time point is different from what I have calculated by hand. It is fairly close to that value. Can someone explain why I have discrepancies here? 3. a R program tech question: I need to extract the p value from the summary(aov.study) but not sure how to do it. looks like the summary is not a data frame or list. I need to take the p value and continue to use it in the R program for some other reports. Thanks much in advance. -- Waverley @ Palo Alto