Mean Confidence Interval Calculator
Build a z-based confidence interval for a mean from mean, known standard deviation, and sample size.
Open toolSTATISTICS
80% Mean Confidence Margin Calculator
Estimate a 80% confidence margin for a mean when population standard deviation is supplied.
Margin1.537862Example result using the prefilled values.
How to use this calculator
Enter Standard deviation, Sample size. The calculator applies the stated relationship and keeps full precision until the displayed result is formatted.
Formula and method
Margin = 1.28155 x sigma / sqrt(n)
The calculator uses the values you enter and evaluates this relationship with standard real-number arithmetic. Intermediate values keep full floating-point precision before the displayed result is formatted.
Worked example
Using the example values already filled into the calculator gives Margin = 1.537862. Change any input to calculate your own result.
Assumptions and limitations
Uses real-number arithmetic and the units stated beside each input. Results are estimates when the inputs are estimates.
Verify important decisions independently and see our methods and limitations.
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