In Figure 4.19, we visually inspected the relative frequency histogram for sample means based on two measurements and noted its bell shape. Another way to determine whether a set of measurements is bell-shaped (normal) is to construct a normal probability plot of the sample data. If the plotted points are nearly a straight line, we say the measurements were selected from a normal population. A normal probability plot was obtained using Minitab software. If the plot-ted points fall within the curved dotted lines, we consider the data to be a random sample from a normal distribution.

a. Do the 45 data values appear to be a random sample from a normal distribution?
b. Using the values of y in Table 4.9, compute the correlation coefficient and p-value for the normal quantile plot to assess whether the data appear to be sampled from a normal distribution.
c. Do the results in part (b) confirm your conclusion from part (a)?

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t--ML Estimates Mean .5 StDev: 1.91485 95- 90- 90 70 50 40 30 20 10- 12