Statistics For Dummies, 2nd Edition
Book image
Explore Book Buy On Amazon

Critical values (z*-values) are an important component of confidence intervals (the statistical technique for estimating population parameters). The z*-value, which appears in the margin of error formula, measures the number of standard errors to be added and subtracted in order to achieve your desired confidence level (the percentage confidence you want). The following table shows common confidence levels and their corresponding z*-values.

Confidence Level z*- value
80% 1.28
85% 1.44
90% 1.64
95% 1.96
98% 2.33
99% 2.58

About This Article

This article is from the book:

About the book author:

Deborah Rumsey, PhD, is an auxiliary faculty member and program specialist in department of statistics at The Ohio State University. An author of several Dummies books, she is a fellow of the American Statistical Association.

This article can be found in the category: