Confidence Interval Calculator
Quick answer: Enter sample data and confidence level (90%, 95%, or 99%) to get the confidence interval and margin of error.
A confidence interval gives a range of plausible values for a population parameter based on sample data. Enter your sample mean, standard deviation, sample size, and desired confidence level to find the interval.
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Last reviewed: April 2026Report an error
Confidence Interval
(94.63, 105.37)
95% CI: (94.63, 105.37), margin of error: ±5.37.
Lower Bound
94.63
Upper Bound
105.37
Margin of Error
±5.37
Standard Error
2.7386
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How to Use This Confidence Interval Calculator
- 1Enter the sample mean.
- 2Enter the standard deviation.
- 3Enter the sample size (n).
- 4Select confidence level: 90%, 95%, or 99%.
- 5Read the lower bound, upper bound, and margin of error.
Frequently Asked Questions
- If you repeated the study 100 times, approximately 95 of the resulting intervals would contain the true population parameter. It does NOT mean a 95% probability the parameter is in this specific interval.
- Larger samples produce narrower confidence intervals (more precise estimates) because the standard error decreases as n increases.
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