A z-test is similar to a t-test. In both cases, the central tendency of a normally distributed sample is compared with either a fixed value or the value of another group.

z-scores indicate the difference between the observed distribution and the comparison in standard deviation units. z-scores derive from the properties of a normal distribution (e.g., 95% of scores will be less than a standardised z-score of 1.96).

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{{Mathematics resources}}