1. 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

2. 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

3. 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