Statistics

Critical Value Calculator

Find the z critical value for a confidence level.

Calculated Output

Critical z-value 1.96

Formula: z = inverse normal of (1 − alpha/tails)

Step-by-Step Breakdown

1. Values used:

2. Confidence level = 95 %

4. Critical z-value = 1.96

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The math behind it

For a z-test it is the inverse normal of 1 − alpha/2 (two-tailed) or 1 − alpha (one-tailed).

95% two-tailed gives z about 1.96.

z or t critical?

Use z for known sigma or large samples; t for small samples with estimated sigma.