Find a confidence interval for a mean from the sample mean, standard deviation, and size. Enter the statistics and pick the confidence.
Confidence Interval
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For the mean.Usage Tip
A wider interval means more confidence but less precision; a larger sample narrows the interval.
THE MATH
interval = mean ± z × (sd ÷ √n)
z from the confidence level
z from the confidence level
A confidence interval is a range likely to contain the true population mean.
At 95 percent confidence, 95 percent of such intervals would capture the true mean.
At 95 percent confidence, 95 percent of such intervals would capture the true mean.
Enter the sample mean, standard deviation, and size.
This uses the normal (z) approximation, best for larger samples.
The margin is z times the standard error.
This uses the normal (z) approximation, best for larger samples.
The margin is z times the standard error.