Chapter 8Minitab Recipe Cards

Confidence intervals for the population mean

• Choose Basic Statistics from the Stat menu and 1-Sample t from the sub-menu.

• In the command window select Summarized data.

• For Example 8.6 enter 40 as the Sample size, 3.47 as the Mean, and 0.82 as the Standard deviation.

• The confidence interval appears in the session window.

Hypothesis tests for differences between population means

• Select Basic Statistics from the Stat menu then 2-Sample t from the sub-menu.

• Click Summarized data. • Type in the Sample size,

Mean and Standard deviation of the ‘own brand’ sample in Example 8.19 (14, 34.9 and 1.4 respectively) in the First row and the equivalent figures for the premium sample (17, 33.4 and 1.1) in the Second.

• For the pooled estimate of the standard error tick Assume equal variances.

• Click Options and check that 0 is in the space beside Test difference.

• Change the Alternative to greater than.

• Click OK.

• The output in the session window includes the test statistic, T-value and the probability that the test statistic occurs if the null hypothesis is true, P-value.

Paired t tests

• Enter the two sets of data in Example 8.20 into C1 and C2.

• Choose Basic Statistics from the Stat menu then Paired t from the sub-menu.

• Check that Samples in columns is selected.

• Type C2 for the First sample and C1 for the Second sample.

• Click Options and specify the null hypothesis value of the mean of the differences, 8, beside Test mean and change the Alternative: to less than.

• The output in the session window includes the test statistic, T-value and the probability that the test statistic occurs if the null hypothesis is true, P-value.