Z-Test Calculator

Your details

Choose based on what you are testing: a single mean, two means, or a proportion.
Two-tailed tests for any difference; one-tailed tests for a specific direction.
The threshold probability below which you reject the null hypothesis.
The average of your sample.
The population mean stated in the null hypothesis.
The population standard deviation, assumed to be known.
Number of observations in your sample.
observations
z-score (test statistic)Not significant
1.6
p-value0.1096
Critical z-value1.96
Standard error2.5
Confidence interval (lower)99.1001
Confidence interval (upper)108.8999
VerdictFail to reject the null hypothesis (p = 0.1096 >= alpha = 0.05)
1.65.5% above · z-score

z = 1.6, two-tailed p = 0.1096, critical z = 1.96. Fail to reject the null.

  • The sample mean sits 1.6 standard errors above the hypothesised population mean.
  • Because p (0.1096) is greater than or equal to alpha (0.05), the result is not statistically significant.
  • The 95% confidence interval for the parameter is [99.1001, 108.8999].
  • Statistical significance is not the same as practical importance. Always report the effect size alongside the p-value.

Next stepConsider whether the sample is large enough to detect the effect size you care about.

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