Free tool
Confidence interval calculator
A mean from its SD and n, or a percentage from a count: the interval, written the way APA 7 asks.
Confidence interval for a mean or a percentage
You get the APA 7 sentence to paste, with the effect size and its confidence interval where one applies.
The full reporting rules, with a worked example, are in the guide on how to report confidence intervals in APA. Have the SPSS output instead? Paste it into the SPSS to APA converter.
Questions
Which method does it use?
For a mean, the t distribution with n - 1 degrees of freedom. For a percentage, the Wilson score interval, which stays between 0% and 100% and is accurate for small samples, unlike the plain normal approximation.
How do I report a confidence interval in APA 7?
Give the level and the limits in square brackets after the estimate, for example M = 100.00, 95% CI [93.81, 106.19].
What does a 95% confidence interval mean?
If the study were repeated many times, 95% of the intervals built this way would contain the true value. A narrow interval means a precise estimate.
Why does n matter so much?
The interval narrows with the square root of n: four times the sample halves its width.