## T-Test and Z-Test Calculation method

This test looks at means that are presented in a row of a table and compares pairs of columns, testing whether the mean in one column is significantly different from the mean in the other column.

By default, OfficeReports is using the Student’s T-Test, compensating for overlap, when test items are represented in both columns compared. Alternatively, OfficeReports can produce the T-Test using Welch’s T-Test. The Welch test does not assume equal variances and computes the df of the test empirically using a function of the group sizes and the variances.

This test looks at the rows of a table independently and compares pairs of columns, testing whether the proportion of respondents in one column is significantly different from the proportion in the other column. The proportion is the count in the cell divided by the base for the column.

In situations where results are weighted, OfficeReports by default uses the Effective Base rather than the simple weighted base in statistical tests on weighted tables. This option has no effect on statistical tests run on unweighted tables. If you want to run the tests on the unweighted data, you must change to Unweighted Base.

The effective base is designed to reduce the likelihood of the statistical tests producing signiﬁcant results because of the adjustments made by weighting; the effective base takes these adjustments into account. The effective base is also a test of how good the weighting is if the weighting is inﬂating the from a particular group by a large factor, the effective base tends to be much smaller than both the unweighted and the weighted base. The closer the effective base is to the unweighted base, the better the weighting is.