18. Machine Breakdowns. To test for any significant difference in the number of hours between breakdowns for four machines, the following data were obtained.

Machine 1 Machine 2 Machine 3 Machine 4 6.4 8.7 11.1 9.9 7.8 7.4 10.3 12.8 5.3 9.4 9.7 12.1 7.4 10.1 10.3 10.8 8.4 9.2 9.2 11.3 7.3 9.8 8.8 11.5

a. At the a = .05 level of significance, what is the difference, if any, in the population mean times among the four machines?

b. Use Fisher’s LSD procedure to test for the equality of the means for machines 2 and 4. Use a .05 level of significance.