 # Chapter 8 Minitab Statistical decision making Confidence intervals

• Slides: 16 Chapter 8 Minitab: Statistical decision making Confidence intervals for the population mean • Choose Basic Statistics from the Stat menu and 1 -Sample t from the sub -menu. • In the top right of the new 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. • Click Options. • In the Options window type 90. 0 in the space to the right of Confidence level. • Click OK then OK in the One-Sample t for the Mean window. • The confidence interval appears in the session window under 90% CI for . Hypothesis tests for differences between population means • Select Basic Statistics from the Stat menu then 2 -Sample t from the sub-menu. • In the new window select Summarized data from the menu to the top right. • For the pooled estimate of the standard error tick Assume equal variances. • Type in the Sample size, Sample mean and Standard deviation of the ‘own brand’ sample in Example 8. 19 (14, 34. 9 and 1. 4) in the Sample 1 boxes and the figures for the premium sample (17, 33. 4 and 1. 1) in the Sample 2 boxes. • Click Options and check that 0 is in the space beside Test difference. • Change Alternative hypothesis to Difference > hypothesized difference. • For the pooled estimate of the standard error tick Assume equal variances. • Click OK then OK in the Two-Sample t for the Mean window. • The output includes the test statistic, T-value and the probability that the test statistic occurs if the null hypothesis is true, the P-value. Paired t tests • Enter the two sets of data in Example 8. 20 into C 1 and C 2. • Choose Basic Statistics from the Stat menu then Paired t from the sub-menu. • Check that Each sample is in a column is selected. • Type C 2 for the location of Sample 1 and C 1 for the location of Sample 2. • Click Options, type 8 as the Hypothesized difference and change the Alternative hypothesis to Difference < hypothesized difference. • Click OK then OK in the Paired t for the Mean window. • The output in the session window includes the test statistic, Tvalue and the probability that the test statistic occurs if the null hypothesis is true, P -value.