Question: An aerospace parts factory has two separate production lines making fasteners; each production line can be regarded as creating a separate population of fasteners, whose widths are normally distributed.  A sample of 20 fasteners is selected from each production line for quality control inspection.  The width of each selected fastener is measured; and the standard deviations s ₁ and s ₂ in the measured widths of the selected fasteners from each production line are calculated.  If the design standard deviation in fastener width for each production line population is unknown, can the sample values s ₁ and s ₂ be used instead? (Points: 3)
Yes
No



4. The US Mint selects ten pennies from the production line to test the hypothesis that the mean weight of each penny is 5 grams.  The normally-distributed weights (in grams) of these pennies are as follows: 1, 5, 8, 4, 8, 4, 9, 2, 6, 8. Assume a = 0.05.
State the null and alternate hypotheses
Calculate the sample mean and standard deviation
Determine which test statistic is appropriate (z or t), and calculate its value.
Determine the critical value(s).
State your decision: Should the null hypothesis be rejected?

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