Confidence Interval Calculator
Enter sample mean, standard deviation, sample size and confidence level to calculate the confidence interval around the mean.
Simplified z-based interval; not suitable for all statistical analyses.
Examples
- Mean 50 units, SD 5, n 30, 95% ⇒ 48.21 to 51.79 units
- Mean 120 units, SD 20, n 100, 90% ⇒ 116.71 to 123.29 units
FAQ
Which confidence levels are supported?
90%, 95%, and 99%; other values default to 95%.
What if sample size is small?
For n<30 consider using the t-distribution.
Does it handle proportions?
No, it is designed for means.
Additional Information
- Uses z-scores assuming normal distribution.
- Larger samples produce narrower intervals.