Hi,

First, I have used the collapse command to make the mean and standard deviation by age and SES for smoking.
Second, I have made the upper and lower values of the confidence interval for smoking.
Third, I have used the command:
xtset SES age

Fourth, I have used the command:
xtline smoking, overlay

Now, I have the figure I am looking for without error bars.
How I can add 95% error bars to each age group across all SES?

I really appreciate your help.