How to use the Confidence Interval Calculator
Estimate margin of error from sample mean, confidence level, standard deviation with the Confidence Interval Calculator. It includes Build confidence interval, Analyze interval bounds workflows, so choose the one that matches the values you actually know. Use it to check the arithmetic while keeping the displayed method and entered values with your work.
Step by step
- For the Confidence Interval, enter sample mean, confidence level, standard deviation, sample size, population size. Keep each value in the unit displayed beside its field.
- Review the selected Confidence Interval workflow and inputs, then read margin of error in the result panel.
- Change one Confidence Interval assumption at a time to compare scenarios. Use Reset to restore this tool's worked example values.
How the calculation works
Builds a normal confidence interval at the selected confidence level, optionally corrects for a finite population, and reports the lower and upper bounds.
Worked example
In the Confidence Interval worked example, sample mean 100, confidence level 95 %, standard deviation 15, sample size 100 produces margin of error of 2.93994598. Build confidence interval: Builds a normal confidence interval at the selected confidence level, optionally corrects for a finite population, and reports the lower and upper bounds. Review the displayed units before comparing the result.
Understanding the result
The Confidence Interval reports margin of error. Use it to check the arithmetic while keeping the displayed method and entered values with your work. The result depends on the entered values, selected mode, and displayed mathematical assumptions.
How to check the answer
Check the Confidence Interval answer by substituting margin of error back into the stated relationship. Test a simple value such as zero, one, or an equal pair, then confirm that sign, scale, units, and rounding match Builds a normal confidence interval at the selected confidence level, optionally corrects for a finite population, and reports the lower and upper bounds.
Common questions
What does the Confidence Interval calculate?
Estimate margin of error from sample mean, confidence level, standard deviation with the Confidence Interval Calculator.
Which Confidence Interval inputs have the biggest effect?
margin of error responds directly to sample mean, confidence level, standard deviation, sample size, population size. Change one input while holding the others constant to see its effect.
Is the Confidence Interval result exact?
The result depends on the entered values, selected mode, and displayed mathematical assumptions. Recheck sample mean, confidence level, standard deviation and use margin of error only for a decision where that level of precision is appropriate.