2x2 table

For 2x2 table ,if expected frequency of each cell is more than 5,and total numbers n>40,we should choose the Peason^，s chi-square test

If expected frequency of any cell1<E<5 and n>40,we should choose Yate^，s continuity correction chi-square test

If E<1 in any cell or n<40 or P value of test is close to the test level,we should use Fisher’s exact test