Generating confidence intervals for a new variable.

[Rowa Taha]

Hi, I have a dataset of outcome measures at difference time points and an anchor score. I want to calculate the 95% CI for difference in means between two groups who score a certain value on an external anchor criterion. the code I am using is below, but the ci command just brings up an error message. Can soemone please assist. PS. I'm a stata novice.




quietly sum pem_change_3mths if groc_3mths==1 | groc_3mths<0
local mean_change = r(mean)
dis `mean_change'

quietly sum pem_change_3mths if groc_3mths==0
local mean_unchanged = r(mean)
dis `mean_unchanged'

local betweenp = `mean_change' - `mean_unchanged'
dis `betweenp'
ci means `betweenp'

[Clyde Schechter]

gen group = 1 if groc_3mths == 1 | groc_3mths < 0
replace group = 2 if groc_3mths == 0
ttest pem_change_3mths, by(group)

The last row of the output table from -ttest- will show you the mean and confidence interval for pem_change_3_mths.

[Rowa Taha]

Thanks so much, that works perfectly! Very much appreciated :-)