Z-test

Z-test

Z-test is based on the normal probability distribution and is used for judging the significance of several statistical measures, particular­ly the mean. The relevant test statistic, z, is worked out and com­pared with its probable value (to be read from table showing area under normal curve) at a specified level of significance for judging the significance of the measure concerned. This is a most frequently used test in research studies. This test is used even when binomial distribution or t-distribution is applicable on the presumption that such a distribution tends to approximate normal distribution as‘n’becomes larger z-test is generally used for comparing the mean of a sample to some hypothesized mean for the population in case of large sample, or when population variance is known. Z-test is also used for judging the significance of difference between means of two-independent samples in case of large samples, or when population variance is known. Z-test is also used for comparing the sample proportion to a theoretical value of population proportion or for judging the difference in proportions of two independent samples when ‘n’ happens to be large. Besides, this test may be used for

judg­ing the significance of median, mode, coefficient of correlation and several other measures.