Testing The Difference Between Two Means

Testing the Difference between Two Means-•What two assumptions must be met when you are using the z test to test differences between two means? Can the sample standard deviations s1 and s2 be used in place of the population standard deviations σ1 and σ2?In order to test a hypothesis successfully, different assumptions are made depending on the test been applied. More so, the assumptions are essential both when choosing a test and / or interpreting results.For example the z-test is based on the following assumption The samples of population been tested are independent and random. Z-test also makes the assumption that the samples taken are normally distributed and the population’s standard deviations are known. The sample data are from normally distributed populations and/ or sample size are large enough such that n1≥30 and n2≥30For example if the population standard deviations σ1 and σ2 are known, then the standard deviation of the sampling distribution of the difference in means D = And In a study with populations n1, n2 such that each population is at least 30, then s1 and s2 can be used in place of σ1 and σ2.Mostly, the conditions for z-test above are not