Statistical Inference

# The Two-Sample Z-Procedures

Please select the aspect of the Two-Sample Z-Procedures you would like practice:

The Two-Sample Z-Procedure is used to compare the means of two populations. Using these procedures, you can calculate a confidence interval for or test a hypothesis regarding that difference, μ1 − μ2. In order to use these procedures, the following assumptions must be met:

1. The data come from a Normal distribution for each population
2. The variances are known for each population

These assumptions are in addition to the usual two assumptions that the samples are representative of the target populations and that the sample values are independent.

If any of these assumptions are not met, then this is not the appropriate procedure to use. Note that the actual first assumptions are that the sample means are Normally distributed. However, since you have but one sample mean, this assumption cannot be directly assessed. An equivalent assumption is that the data are from a Normal distribution, which can be tested.