Hi statalisters,

I have question about interpreting the retransformed coefficient in a regression analysis.

I'm analyzing a biomarker which is sampled 2-3 times for approximately 30 patients (total 80 observations). The biomarker is not normally distributed, and therefore I calculated the square root of it. Then I performed a linear regression analysis, and now I have a hard time interpreting the data. I'd like to estimate the average % increase of the biomarker per year, but I'm not sure I can trust the results.

My code looks like this:

gen biomarker2 = sqrt(biomarker)
reg biomarker2 time, vce(cluster patientid)

Taking the coefficient^2 would yield the retransformed coefficient, right? But then I'd like to see the average increase in % per year. Can I just calculate (retransformed coefficient)/intercept, or do I need to retransform the intercept too? What if I'd like to see the average per month - can I divide the increase by 12? Or does not any of this make sense?

Many thanks in advance,
Gunnar