Critical Value Calculator
Find the critical value for z, t, chi-square, or F distributions.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Select the distribution type, enter the significance level (alpha), add degrees of freedom for t-distribution, and choose one-tailed or two-tailed. The calculator returns the critical value.
About This Calculator
A critical value is the threshold that a test statistic must exceed to reject the null hypothesis. For a two-tailed test at alpha = 0.05, the z critical value is 1.96. Critical values depend on the distribution, significance level, tail type, and degrees of freedom.
Frequently Asked Questions
What is the most common critical z-value?
For a two-tailed test at the 5% significance level, the critical z-value is 1.96. For one-tailed at 5%, it is 1.645.
How do degrees of freedom affect the t critical value?
Fewer degrees of freedom produce larger critical values (wider tails). As df increases, the t-distribution approaches the normal distribution.
When do I use a one-tailed vs two-tailed test?
Use one-tailed when you have a specific directional hypothesis (e.g., "greater than"). Use two-tailed when testing for any difference.