Business Statistics

A student team in a business statistics course conducted an experiment to test the download times of the three different types of computers (Mac, iMac, and Dell) available at the university library. The students randomly selected one computer of each type. The students went to the Microsoft game Web site and clicked on the download link for the NBA game. The time (in seconds) between clicking on the link and the completion of the download was recorded. After each download, the file was deleted, and the trash folder was emptied. A total of 30 downloads were completed in random order. The results are shown below. NOTE: You can copy and paste the data into Excel/PHStat.
 

Mac iMac Dell
156 160 236
166 165 238
148 184 257
160 192 242
139 197 282
151 172 253
158 189 270
167 179 256
142 200 267
219 193 259
 

a. One assumption of ANOVA is that the data are approximately normally distributed. Do the download times for each type computer appear to be approximately normally distributed? Support your answer with appropriate calculations or graphs.

b. Another assumption of ANOVA is that the variances of the populations are equal. At the .05 level of significance, is there evidence of a difference in the variations in the download times for the three types of computers?
Complete the following:
1. State H0.
2. State H1.
3. State the value of α.
4. State the value of the test statistic.
5. State the p-value.
6. State the decision in terms of H0 and why.
7. State the decision in terms of the problem. 

c. At the .05 level of significance, is there evidence of a difference in the mean download times for the three computers?
Complete the following:
1. State H0.
2. State H1.
3. State the value of α.
4. State the value of the test statistic.
5. State the p-value.
6. State the decision in terms of H0 and why.
7. State the decision in terms of the problem. 

d. If appropriate, use the Tukey-Kramer procedure to determine which download times differ significantly.

e. Based on the above, which computer should be chosen if you are interested in the shortest download time?