Calculated column with condition returns wrong results (DAX)

Hello, I am trying to use a seemingly straightoforward condition to calculate a new column but I keep getting unexpected results. My database is fairly large but I have created a small dataset where the same issue occurs.

Here's my example:

I have the following two columns

I then created a New Measure:

Measure2=AVERAGE(Sheet11[Test2])

(i.e. the average of my second column, the answer being 5)

I then added a New Column:

Column=if(Sheet11[Test1]>=[Measure2],"Success")

I expected this to show Success to all values in column Test1 that are 5 or above. However, this is what I get:

... which doesn't make any sense!!

Am I missing something blatantly obvious? Any help much appreciated!!