z-score equation (find z)

$z = ( "x" - mu ) / sigma$

$(x) "Individual value from set of data"$

$(u) "Population mean"$

$(o) "standard deviation of population"$

Tags

In statistics, the z-score is the number of standard deviations an observation or datum is above or below the mean. A positive standard score indicates a datum above the mean, while a negative standard score indicates a datum below the mean. It is a dimensionless quantity obtained by subtracting the population mean from an individual raw score and then dividing the difference by the population standard deviation; this conversion process is called standardizing, or nominalizing. Standardized scores are useful because they have the same meaning universally.

Additional Resources

This equation gives you a z-score for any individual value. To find the a value given a z-score, click .

References

Gravetter, F. J., & Wallnau, L. B. (2013). Statistics for the Behavioral Sciences. Wadsworth, CA: Cengage Learning.

Open Source: wikipedia.org/wiki/Standard_score