Calculate mean by ID number

Hi,

I have a 3000+ row data set with two columns: StationID and DIN (dissolved inorganic nitrogen if anyone is curious). There are 166 stations, and I would like to get the mean DIN value of each station.

The data is set up like this:

StationID, DIN
1, 10.1
1, 12.2
1, 13.1
2A, 3.4
2A, 3.2
6012, 5.6
6012, 6.7
6012, 6.7
6012, 5.9

So, my main issue is that there are a variable number of DIN readings for each station, and the stations do not follow a pattern (some have letters, not consecutive numbers, etc).

Is there a good way of going about this?

Thanks

Edit. Thanks!

if you put the stations in a list then you could use averageif()
=AVERAGEIF(A:A,E2,B:B)

see attached