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Dear experts I have some questions with regard to covariate treatment in the statistical model and multiple regressions: I would like to find out if the covariate "age" has an influence in my experiment. How do I use a two-sample t-test with age as a covariate? Can I do it without using a full factorial design? In which I define 2 factors: group and age. Another question is about multiple regressions; we used a design matrix of multiple regressions in order to find out whether protein levels influence the brain activity. We used 3 contrasts: Group: 1 0 Positive: 0 1 Negative: 0 -1 Is that the right way to do it? Also, we can use some help in interpretation of the results: Would it be correct to say that regions that are negatively correlated with the protein level, means that these areas have decreased activity the more protein exist? And visa verse for areas positively correlated with the protein level? Finally, the results show that there is laterality in activation, meaning that there is a positive correlation between the left hemisphere and protein level, and negative correlation to the right hemisphere. Looks weird. Can these be due to a mistake in our method? Thank you in advance for your help. Reut