90% Confidence Interval: Mean 25, SD 5, n = 25
With mean 25, SD 5, and sample size 25, the 90% confidence interval (Z* = 1.645) ranges from about 23.36 to 26.64.
How to use this tool
- Enter sample mean (x̄), sample standard deviation (s), sample size (n) and z* (confidence level) in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your lower bound and the full breakdown beneath it.
Compute the 90% confidence interval for a sample of 25 observations with mean 25 and standard deviation 5.
Frequently asked questions
- How do I choose the z* value?
- Common critical z-values: 1.645 for 90% confidence, 1.960 for 95%, 2.576 for 99%. These assume a large enough sample (n ≥ 30) so the Central Limit Theorem applies.