Fisher Exact Test Calculator Formula

Understand the math behind the fisher exact test calculator. Each variable explained with a worked example.

Use the Fisher Exact Test Calculator

Formulas Used

Odds Ratio

odds_ratio = (a * d) / max(b * c, 0.0001)

Total N

n = a + b + c + d

Row 1 Total

row1 = a + b

Row 2 Total

row2 = c + d

Variables

VariableDescriptionDefault
aCell a (R1,C1)8
bCell b (R1,C2)2
cCell c (R2,C1)3
dCell d (R2,C2)7

How It Works

Fisher Exact Test

Computes exact probability for 2x2 tables. Preferred over chi-square for small samples.

Worked Example

2x2: a=8, b=2, c=3, d=7.

a = 8b = 2c = 3d = 7
  1. 01OR = 56/6 = 9.33
  2. 02N=20

Ready to run the numbers?

Open Fisher Exact Test Calculator