Confidence Interval Calculator

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Calculates the range within which a population parameter (e.g., mean, proportion) is likely to lie, with a certain confidence level.

How To Use

How to use this calculator

Start with your values, or try a preset.

Step 1

Enter Sample Mean, Sample Standard Deviation, Sample Size, and Confidence Level (%) in the units shown.

Step 2

Read Z-Score, Standard Error, Margin of Error, Upper Bound, and Lower Bound in the results panel. Results update as you change the inputs.

Step 3

Choose a preset to load an example, then adjust the values for your situation.

Worked Examples

See the inputs and their calculated results.

Sample Mean: 50; Sample Standard Deviation: 10; Sample Size: 30; Confidence Level (%): 95 %

Z-Score: 1.96; Standard Error: 1.825741858; Margin of Error: 3.578454042; Upper Bound: 53.57845404; Lower Bound: 46.42154596

Sample Mean: 75; Sample Standard Deviation: 15; Sample Size: 50; Confidence Level (%): 90 %

Z-Score: 1.645; Standard Error: 2.121320344; Margin of Error: 3.489571965; Upper Bound: 78.48957197; Lower Bound: 71.51042803

Sample Mean: 100; Sample Standard Deviation: 20; Sample Size: 100; Confidence Level (%): 99 %

Z-Score: 2.576; Standard Error: 2; Margin of Error: 5.152; Upper Bound: 105.152; Lower Bound: 94.848

Explore the topic

Use calculators for algebra, geometry, trigonometry, probability, statistics, averages, z-scores, tests, and graphing tasks.

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