# Why should I use a 1 variance test?

To perform this test, select Stat > Basic Statistics > 1 Variance.

Use the 1 Variance test to estimate the variance or the standard deviation of a population and compare it to a target or reference value. Using this test you can:
• Determine whether the variance or the standard deviation of a group differs from a specified value.
• Calculate a range of values that is likely to include the population variance or standard deviation.

For example, you receive a shipment of unprocessed lumber and you want to assess whether the moisture content is too variable.

For 1 Variance, the hypotheses are:
Null hypothesis
 H0: σ = σ0 The population standard deviation (σ) equals the hypothesized standard deviation (σ0).
Alternative hypothesis
Choose one:
 H1: σ ≠ σ0 The population standard deviation (σ) differs from the hypothesized standard deviation (σ0). H1: σ > σ0 The population standard deviation (σ) is greater than the hypothesized standard deviation (σ0). H1: σ < σ0 The population standard deviation (σ) is less than the hypothesized standard deviation (σ0).
###### Note

If you are testing the variance, substitute variance (σ2) for standard deviation (σ) in the hypotheses.

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