Nonparametric Methods in Statistics with SAS Applications

FISHER EXACT TEST 65

the alternative hypothesis is that column proportions are not all equal. For a single

sample, the null hypothesis is that there is no association between the measured vari-

ables (i.e., they are independent), whereas the alternative hypothesis states that an

association exists.

The assumption of validity of the chi-square test is that the expected count under H

0

for each cell in a contingency table is at least 5. The expected count in a cell is de-

fined as the product of the corresponding marginal totals divided by the grand total.

If this assumption is violated and some expected counts are below 5, a nonparamet-

ric Fisher exact ...