How to take mean of columns based on DateTime?

[#1]

Greetings!

I have a large dataset, a snippet of which looks like this: 

I want to take the mean of each of the 7 P-P and RMS columns that have the same DateTime.  Since there are 4 unique DateTimes in the data, this would result in a table with 4 rows.  Ideally SN column would be preserved.  I suspect Tables->Summary may hold the key, but I can't get it to do what I want.  I have been able to get the result I want using Formula columns, but this is a frequent need with lots more columns and Formula columns get cumbersome quickly.

Thank you!

Andy

[#2 · Accepted solution]

Summary (or tabulate) should work. What issues are you having with Summary table?

[#3]

Thank you. Your example made it clear.  I was dropping the wrong columns in the wrong boxes.

[#4]

One suggestion I have is to check the "Keep Dialog Open". Then just try dropping different columns to different places to see what happens, for example move SN to Subgroup instead of Group. Having enabled "Keep Dialog Open" makes it much easier and faster to test different approaches. Sometimes "Help" button is also very useful and will provide explanations and examples.