To determine whether which company makes auto batteries affects the average length of life of the battery, the sample data in the file titled Start were obtained.

The data represent the lengths of life (months) for batteries of the same specifications for each of three manufacturers.

a. Determine if the average length of battery life is different among the batteries produced by the three manufacturers. Use a significance level of 0.05.

b. Which manufacturer produces the battery with the longest average length of life? If warranted, conduct the Tukey-Kramer procedure to determine this. Use a significance level of 0.05. (Note: You will need to manipulate the data columns to obtain the appropriate factor levels.)