How would I go about finding the median of a row for each of another row in my Dataframe?

Sorry about the confusing phrasing, I have a dataframe with a variable called test_id. The dataframe looks something like this:

I would like to find the median of the number row, but for each test id. I have tried a few ways but none have worked, and rounding has confused me.

I would like my final result to look like this:

Sorry if this is a simple question, I am relatively new to pandas and dataframes in general.