I am confused as to how I was meant to know E for a X^2 test in the following question:
2.i and 2.ii give no more information.
Not knowing what to do I used E as 0 for the first row and 40 (3+37) for the second row, but that was just a guess. It was wrong and the correct answer for E is 20.
I suspect this has something to do with the 20 fields but I can't beleive that I'm just meant to know they expect one butterfly per field...
How was I meant to know E?