The Mean Length of a Small Counter Balance Bar Is

question 97

Multiple Choice

The mean length of a small counter balance bar is 43 millimeters. There is concern that the
Adjustments of the machine producing the bars have changed. Test the claim at the 0.02 level that
There has been no change in the mean length. The alternate hypothesis is that there has been a
Change. Twelve bars (n = 12) were selected at random and their lengths recorded. The lengths are
(in millimeters) 42, 39, 42, 45, 43, 40, 39, 41, 40, 42, 43 and 42. The mean of the sample is 41.5 and
The standard deviation 1.784. Computed t = -2.913. Has there been a statistically significant change
In the mean length of the bars?

• A) Yes, because the computed t lies in the area beyond the critical.
• B) No, because the information given is not complete.
• C) No, because the computed t lies in the area to the right of -2.718.

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