Obtaining a 95% Tolerance Interval for 2 separate groups

Hi, I am extremely new to R and would really appreciate any help anyone can offer!!
I am trying to compare the outcome of the treatment vs control group. I have the data frame regarding cystic fibrosis lung capacity which includes the pre vs post intervention values.

I have split the data frame into 2 Regimes (treatment & control). I am using the following code to get the tolerance interval of improvement however it's for the entire population of the experiment.

normtol.int(CF.df$Improvement, alpha = 0.05, P = 0.95, side = 2)

Does any one know how I can get this function to take into account the 2 distinct groups (control and experiment) as I need to obtain a 95% tolerance interval of improvement over the duration of the experiment for each group

Hi, welcome to the forum.

I think we need a FAQ: How to do a minimal reproducible example ( reprex ) for beginners

A handy way to supply some sample data is the dput() function. In the case of a large dataset something like dput(head(mydata, 100)) should supply the data we need.