A confidence interval for a difference in proportions is a range of values that is likely to contain the true difference between two population proportions with a certain level of confidence.
The formula to calculate the confidence interval is:
Confidence interval = (p1 – p2) +/- z*√(p1(1-p1)/n1 + p2(1-p2)/n2)
- p1, p2: sample 1 proportion, sample 2 proportion
- z: the z-critical value based on the confidence level
- n1, n2: sample 1 size, sample 2 size
To find a confidence interval for a difference between two population proportions, simply fill in the boxes below and then click the “Calculate” button.
95% C.I. = [0.0236, 0.2964]
You can be 95% confident that the interval [0.0236, 0.2964] contains the true difference between the population proportions.