- Thread starter JillthePill
- Start date

Lets say have 1 control and 5 treatment groups. you run 5 comparison tests between the control and the treatments, each at an alpha of 0.10, then the total alpha risk is 1-(1-0.10)^5 = .40951 . If you used an alpha of .021 for each of the 5, then you total alpha risk would be 0.10.

Also, I would not make the degrees of freedom assumption unless the Satterwaite degrees of freedom are more than 100. How many trees in each group? If over 100 each then its an okay assumption.

Sorry to add more items to think about, but I guess thats the nature of this board.

As for the alpha risk, you'd have to see the context. I truly only care about the pairwise comparison. I only want to know: is, say, the mean at 900 m^2 significantly different from the mean at 400 m^2 in isolation without caring about the other cases at the moment.

My advisor now says I have t wrong for 2-tails, and it should be 1.64. Should be an easy fix.