A manufacturer of cases for sound equipment requires that holes be drilled for metal screws. The drill bits wear out and must be replaced; there is expense not only in the cost of the bits but also in the cost of lost production. Engineers varied the rotation speed of the drill and measured the lifetime y (thousands of holes drilled) of four bits at each of five speeds x. The data were:

a. Create a scatterplot of the data. Does there appear to be a relation? Does it ­appear to be linear?
b. Is there any evident outlier? If so, does it have high influence?

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60 0 60 60 80 0 80 80 100 100 y 4.6 38 4.9 45 4.7 58 5.5 5.4 5.0 4.5 x 100 100 120 20 120 120 140 140 140 140 y 3.2 4.8 4. 45 4.0 8 3.6 3.0 3.5 3.4