Two solutions are proposed for the estimation of odds ratios (OR) when one or the two elements of the principal (A, D) or secondary (B, C) diagonals of a 2 x 2 matrix (A, B, C, D) are 0. The OR estimate is AD/BC. If A or D are 0, OR = 0; if B or C are 0, the OR is undefined.
Can you use Fisher exact test with 0?
The Fishers exact test is one of the Chi-2 family tests that examines the association or independence of the two quantities grouped by each other. Its use is also when the number of data in a group is at least equal to that of the other table cells. So you can use this test when faced with a zero value in a group.
What is the odds ratio division by zero?
Any positive number divided by zero is infinite. So simply state that the odds ratio is infinity. Go ahead and use the word, infinity, an abbreviation like Inf, or that sideways 8 symbol. Then use Fisher's Exact test to calculate the statistical significance.
What is the odds ratio in the Fisher test?
The odds ratio mostly works on nominal variables that have exactly two levels. The statistical test called Fisher's Exact for 2x2 tables tests whether the odds ratio is equal to 1 or not. It can also test whether the odds ratio is greater or less than 1.
What are odds of zero?
A probability of 0 is the same as odds of 0. Probabilities between 0 and 0.5 equal odds less than 1.0. A probability of 0.5 is the same as odds of 1.0. Think of it this way: The probability of flipping a coin to heads is 50%.
How do you interpret the odds ratio in chi-square?
This effect size is traditionally interpreted as like likelihood of group 1 to group 2. Therefore, an odds of 1 indicates they are equally likely. Odds less than 1 indicate that group 2 is more likely, and odds greater than 1 indicate that group 1 is more likely.