Confidence Interval Calculator
Calculate a two-sided normal confidence interval for a mean with a transparent formula trace.
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What Is the Confidence Interval Calculator?
The Confidence Interval Calculator uses the sample mean, standard deviation, sample size and selected normal critical value to report the interval, margin and standard error.
How It Works
Enter the summary statistics and confidence level. Review whether a normal z interval matches the study design.
When to Use It
Use it for quick descriptive analysis when the sample and distribution assumptions support a z interval.
Frequently Asked Questions
- When Is A t Interval Better?
- A t interval is commonly preferred for smaller samples when the population standard deviation is unknown.
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