T-test: ratios or log ratios - (Apr/30/2012 )

Quick question, when comparing between 2 groups ---> before and after treatment in test & control groups, I understand that I should use unpaired t-test. In the graph I present the data as log2 ratio to visualize the increase/decrease following treatment. But for statistical analysis, should I use mean of log2 ratio or mean of actual ratios since when I tried both give different p-values? Which one is more appropriate? Thank you.

Use your raw data or transformed raw data (if no normal distribution) but not the means.

but what if i want to compare the response (ratio) between these 2 groups? Unpaired t-test will compare means (correct me if I'm wrong) so I wonder if it's appropriate to use transformed data (log ratio instead of actual ratio) to get the mean?

yes it does, but your post sounded as if you just want to use the means as input for the test.
Anyway the before-after treatments are paired data and I'd test them either separately using raw data with a paired t-test or using ratios with the ratio paired t-test as offered by some software (e.g. graphpad, prism). The normal student's t-test I would not use for ratio data as they're not normal distributed. If not possible to use the ratio test, use the non-parametric alternative the Mann-Whitney U Test...

I understand now. Thanks!
btw, sorry for the misunderstanding. non-native speaker's here