# The Sample Size Calculator - Estimating Mean

This calculator helps you find the appropriate sample size for estimating the mean of a population that’s normally distributed within a specified margin of error.

You need to provide the confidence interval, the margin of error, and the population standard deviation (σ) below and click the ‘Calculate’ button:

Usually 90%, 95%, or 99%

Assuming the population standard deviation to be 10, you need a sample size of:

171

to estimate a mean with 95% confidence and a precision of 1.5

The confidence interval is usually 90%, 95%, or 99%.

The formula to calculate the sample size is:

``````n = (Zα/2σ/E)2
``````

Where `n` is the sample size, `Zα/2` is the z critical value, `E` is the margin of error, and σ is the population standard deviation.

I hope this calculator is useful. Happy analyzing!

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