A confidence interval for a difference between means is a range of values that is likely to contain the true difference between two population means with a certain level of confidence.
The formula to calculate the confidence interval is:
Confidence interval = (x1–x2) +/- t*√((sp2/n1) + (sp2/n2))
- x1, x2: sample 1 mean, sample 2 mean
- t: the t-critical value based on the confidence level
- sp2: pooled variance
- n1, n2: sample 1 size, sample 2 size
To find a confidence interval for a difference between two means, simply fill in the boxes below and then click the “Calculate” button.
95% C.I. = [-2.0049, 3.6049]
You can be 95% confident that the interval [-2.0049, 3.6049] contains the true difference between the population means μ1 and μ2.