### Glossary terms for 'Z'

Z test | A statistical test used to compare proportions to determine if they are statistically significantly different from one another. Unlike the Chi-squared test, which is always 2-sided, the Z test can be used for one-sided hypotheses. For example, a one-sided Z test could be used to determine if the proportion of prisoners who have diabetes is significantly greater than the proportion of free-living persons who have diabetes. Similarly, a two-sided Z test (or Chi-squared test) could be used to determine if the proportion of prisoners who have diabetes is significantly different (i.e., smaller or larger) than the proportion not in prison who have diabetes. |

Glossary material from Hulley SB et al. *Designing Clinical Research*, 4th ed. Philadelphia, Lippincott Williams & Wilkins, 2013.