Examining Two Proportions Special Topics 504: Practical Methods in Analyzing Animal Science Experiments Examining Two Proportions Fisher’s exact test: p = (a + b)! (c + d)! (a + c)! (b + d)! a! b! c! d! Chi square (χ2)test: p = Σ (observed – expected)2 expected

Examining Two Proportions Special Topics 504: Practical Methods in Analyzing Animal Science Experiments Examining Two Proportions Contingency table:   Sample1 Sample2 Trmt 1 a b a + b Trmt 2 c d c + d a + c b + d

Examining Two Proportions Special Topics 504: Practical Methods in Analyzing Animal Science Experiments Examining Two Proportions Contingency table examples:   Females Males total Treated 4 10 14 Control 6 7 13 17 27   CWD Healthy total Treated 34 88 122 Control 13 29 42 47 117 164