The tire wear of n1 5 n2 5 100 tires of two types in Example 8.9 had sample means and standard deviations shown in the table. Is there evidence of a difference in the tire wear for the two types of tires?

1. Select stat ➤ TESTS ➤ 3:2-SampZTest… Select Stats in the “Inpt:” line, and enter the values for n1, n2 , 1 x , and 2 x on the appropriate lines. Enter the value for s =1200 1 and s =1400 2 on the lines marked s1 and s2. (Notice that we are assuming that the population standard deviations, s1 and s2, can be approximated by s1 and s2.)
2. Make sure that the alternative hypothesis is set to m ≠ m0 . When you move the cursor to Calculate and press Enter, the results will appear, shown on the screen in Figure 9.18(b). With z =7.05 and p-value 50.000, the results are highly significant, and there is evidence of a difference in the tire wear for the two types of tires.

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Type 1 Type 2 Sample Mean 26,400 miles 25,100 miles Sample Standard Deviation 1200 miles 1400 miles