67.02 to 68.98
Confidence Interval Calculator
Use this free confidence interval calculator to find z confidence intervals for a mean or proportion with margin of error, standard error, point estimate, steps, copy, and history.
Formula steps Examples included Copy results Private history
95% confidence interval67.02 to 68.98
- Margin
- 0.98
- Z-score
- 1.96
- Point estimate
- 68
How to use the confidence interval calculator
- Choose mean interval or proportion interval mode.
- Choose a confidence level, then enter the sample values requested for that mode.
- Press Calculate interval to see the lower bound, upper bound, margin of error, and steps.
- Use examples, recent answers, or copy the interval while checking estimates.
Common uses
Calculate a confidence interval for a mean using standard deviation and sample size.
Calculate a confidence interval for a sample proportion.
Compare common confidence levels from 80% through 99%.
Copy the interval, margin of error, z-score, and point estimate.
Examples
42.2% to 61.8%
67.1775 to 68.8225
Frequently asked questions
Quick answers about formulas, inputs, examples, result copying, and private in-browser history.
What is a confidence interval?
A confidence interval is a range around a sample estimate that is built to capture a population value at a chosen confidence level.
What interval types are supported?
This version supports z intervals for a single mean and a single proportion.
What is margin of error?
Margin of error is the amount added to and subtracted from the point estimate to create the lower and upper bounds.
Should I use mean or proportion mode?
Use mean mode for numeric averages. Use proportion mode for successes out of a total, such as yes responses or defect counts.
Can this replace advanced statistical software?
No. It is a quick educational calculator for common z intervals. Advanced studies may need t intervals, design effects, or exact methods.
Is my confidence interval history private?
Yes. Recent confidence interval answers stay only in the current browser tab while you use the page. They are not sent to a server.
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