Z Critical Value Calculator

Critical Value of Z (Right Tailed): 1.65
Critical Value of Z (Two Tailed): ± 1.96

Tool Overview: Z Critical Value Calculator

Stuck trying to interpret the results of a statistical test - specifically finding the critical values for a standard normal distribution? You've come to the right place. Our free statistics package is intended as an alternative to Minitab and other paid software. This particular calculator generates the critical values for a standard normal distribution for a given confidence level. The critical value is the point on a statistical distribution that represents an associated probability level. It generates critical values for both a left tailed test and a two-tailed test (splitting the alpha between the left and right side of the distribution). Simply enter the requested parameters (alpha level) into the calculator and hit calculate.

How To Find Critical Values of Z

This calculator is intended to replace the use of a Z score table while providing access to a wider range of possible values for you to work with. In the offline version, you use a z score table to look up the critical value for the test based on your desired level of alpha. Remember to adjust the alpha value based on wether you are doing a single-tailed test or two tailed test. In this case, we can simply split the value of alpha in two since the standard normal distsribution is symmetric about its axis. From there, finding the critical values for your test is a matter of looking up the appropriate row and column in the table. Our critical values calculator automates this process, so all you need to do is enter your alpha value and the tool will find the critical values for you.

When to Use Standard Normal (Z) vs. Student's T distribution

This calculator requires you to have sufficiently large sample that you are comfortable the values of the mean will converge on the standard normal distribution via the central limit theorem. This genreally requires you to have 30+ observations. If you are working with a smaller sample, you should consider using the version we set up to find critical values of a t-distribution.

About this Website

This calculator is part of a larger collection of tools we've assembled as a free replacement to paid statistical packages. The other tools on this site include a descriptive statistics tool, confidence interval generators (standard normal, proportions), linear regression tools, and other tools for probability and statistics. Many calculators allow you to save and recycle your data in similar calculations, saving you time and frustration. Bookmark us and come back when you need a good source of free statistics tools.

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