Question

The postal service sorts mail as Priority Mail Express, Priority Mail, First-Class Mail, or Standard Mail. Over a period of 3 weeks, 18 of each type were mailed from the Network Distribution Center in Atlanta, Georgia, to Des Moines, lowa. The total delivery time in days was recorded. Minitab was used to perform the ANOVA. The results follow: DF Source Factor Error Total P 0.021 SS 3.03 19.94 22.97 MSF 1.01 3.48 0.29 68 Level Priority Mail Express Priority Mail First-Class Mail Standard Mail N 18 18 18 18 Mean 2.890 2.978 3.413 3.216 StDev 0.434 0.678 0.602 0.403 Using the ANOVA results, compare the average delivery times of the four different types of mail. 1. Identify the null hypothesis and the alternate hypothesis. Null hypothesis: a. Ho: M1 + H2 H3 € M4 b. Ho: V1 = 42 = 43 = 4 2. Alternate hypothesis: OH: At least one mean is different. OH: All means are equal. 3. Use the 0.05 significance level to test if this evidence suggests a difference in the means for the different types of mail. HO is .There is in the means for the different types of mail.

Answer 1

1. Null hypothesis: ; Option B is correct.

Ho: M1 = M2 = M3 = M4

2. Alternate hypothesis: H1: At least one mean is different. Option A is correct.

3. p - Value = 0.021 which is less than 0.05. Hence,

Ho is rejected. There is sufficient evidence to suggest a difference in means for the different types of mail.