Mean interval
Mean 68, SD 3, n=36, 95%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.
Inputs to check Example numbers Copyable answer Tab-only 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.
What people use it for
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.
Quick examples
Proportion interval
52 successes, n=100, 95%42.2% to 61.8%
Narrower level
Mean 68, SD 3, n=36, 90%67.1775 to 68.8225
Need the guide or a nearby tool?
Need a slower walkthrough, a related calculator, or the full library? These links keep you close to the task you started.
- How to use the Confidence Interval Calculator See slower examples, input meanings, formula notes, result limits, and mistakes to avoid.
- Calculators Browse related calculators and utilities in the same category.
- Calculator and utility guides Find more guides that use real tool inputs and example numbers.
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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 do the main Confidence Interval Calculator inputs mean?
The main inputs are the numbers, operation, mode, or known values the calculator needs. Keep units consistent, enter percentages the way the page label shows, and use the examples as a quick check before trusting the answer.
How should I read the Confidence Interval Calculator answer?
Read the headline answer, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.
What should I double-check before trusting the Confidence Interval Calculator?
Check units, signs, rounding, and the selected mode before copying the answer. If the number feels weird, rerun one of the examples first, then put your own values back in slowly.
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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