An automobile manufacturer is interested in the fuel efficiency of a proposed new car design. Six nonprofessional drivers were selected, and each one drove a prototype of the new car from Phoenix to Los Angeles. The resulting fuel efficiencies (x, in miles per gallon) are:

The normal scores for a sample of size 6 are
21.282 20.643 20.202 0.202 0.643 1.282
a. Construct a normal probability plot for the fuel efficiency data. Does the plot look linear?
b. Compute the correlation coefficient for the (normal score, x) pairs. Compare this value to the critical r value from Table 6.2 to determine if it is reasonable to think that the fuel efficiency distribution is approximately normal.

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27.2 29.3 31.2 28.4 30.3 29.6