Machine Breakdowns The number of machine breakdowns per month was recorded for 9 months on two identical machines, A and B, used to make wire rope:
Month | A | B |
1 | 3 | 7 |
2 | 14 | 12 |
3 | 7 | 9 |
4 | 10 | 15 |
5 | 9 | 12 |
6 | 6 | 6 |
7 | 13 | 12 |
8 | 6 | 5 |
9 | 7 | 13 |
a. Do the data provide sufficient evidence to indicate a difference in the monthly breakdown rates for the two machines? Test by using a value of a near .05.
b. Can you think of a reason the breakdown rates for the two machines might vary from month to month?
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