99% Confidence Interval: Mean 100, SD 20, n = 200
With mean 100, SD 20, and n = 200, the 99% confidence interval (Z* = 2.576) is approximately 96.36 to 103.64.
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.
Calculate the 99% confidence interval for a sample of 200 with mean 100 and standard deviation 20.
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.