A manufacturer of industrial light bulbs likes its bulbs to have a mean length of life that is acceptable to its customers and a variation in length of life that is relatively small.
A sample of 20 bulbs tested produced the following lengths of life (in hours):

The manufacturer wishes to control the variability in length of life so that s is less than 150 hours. Do the data provide sufficient evidence to indicate that the manufacturer is achieving this goal? Test using α = .01.

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