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Ztest
Explanations > Social Research > Analysis > Ztest Description  Discussion  See also
DescriptionThe Ztest compares sample and population means to determine if there is a significant difference. It requires a simple random sample from a population with a Normal distribution and where where the mean is known. CalculationThe z measure is calculated as: z = (x  m) / SE where x is the mean sample to be standardized, m (mu) is the population mean and SE is the standard error of the mean. SE = s / SQRT(n) where s is the population standard deviation and n is the sample size. The z value is then looked up in a ztable. A negative z value means it is below the population mean (the sign is ignored in the lookup table). DiscussionThe Ztest is typically with standardized tests, checking whether the scores from a particular sample are within or outside the standard test performance. The z value indicates the number of standard deviation units of the sample from the population mean. Note that the ztest is not the same as the zscore, although they are closely related. See also 

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