Fisher Exact Test

Consider two dichotomous tests: [1 | 2] and [A | B] applied to a sample of size N. Display the number of (A1), (B1), (A2), (B2) cases in a 2x2 contingency table:
        A   B
    1   a   b
    2   c   d
If the tests are independent, ratios should be equal (e.g., a/c = b/d )... They rarely are equal, so the question is: are the ratios different enough to reject the hypothesis of independence.

In the below table fill in the required values. All entries should be whole numbers!

a= b= c= d= number of (A1) cases= a number of (B1) cases= b number of (A2) cases= c number of (B2) cases= d