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, Iowa. The total delivery time in days was recorded. Minitab was used to perform the ANOVA. The results follow:

Using the ANOVA results, compare the average delivery times of the four different types of mail.

Analysis of Variance Ad SS Ad MS F-Value 3 36.7878 Source P-Value 13.62 0.0001 DF Factor 11.9226 68 59.5167 Error 0.8762 Tatal 71 95.2844 Model Summary R-sq A-sq(ad) R-sqlpred) 34.78% 0.935545 37 54% 29.97% Means Factor Mean StDev 956 CI Priority Mall Expresa 18 1.2556 0.6271 (0.8156, 1.6956) 18 1.9944 0.9434 (1.5544, 2.4345) 1.0800 (2.4211, 3.3011) Priority Mall First-Class Mail 18 2.8611 Standard Mail 3.0000 18 1.0460 (2.5600, 3.4400) Pooled SIDev = 0.935545 Fisher Individual Tests for Differences of Means SE of Difference Difference of Means T-Value Adjusted P-Value Diflerence of Levels 95% CI Priority Mail-Priority Mail Express First-Clase Mail-Priority Mail Exprees Standard Mail-Priority Mail Express 0.7389 0.3118 (0.1186, 1.3612) 2.37 0.0207 1.6056 0.3118 (0.9833, 2.227B) 6.15