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What is the Z critical value for 95% confidence?
The Z critical value for a 95% confidence interval is:
- 1.96 for a two-tailed test;
- 1.64 for a right-tailed test; and
- -1.64 for a left-tailed test.
Is a t critical value the same as Z critical value?
In theory, no. In practice, very often, yes. The t-Student distribution is similar to the standard normal distribution, but it is not the same. However, if the number of degrees of freedom (which is, roughly speaking, the size of your sample) is large enough (>30), then the two distributions are practically indistinguishable, and so the t critical value has practically the same value as the Z critical value.
What is a Z critical value?
A Z critical value is the value that defines the critical region in hypothesis testing when the test statistic follows the standard normal distribution. If the value of the test statistic falls into the critical region, you should reject the null hypothesis and accept the alternative hypothesis.