Problems 34 and 35 each include a normal probability plot and either a frequency histogram or a stem-and-leaf diagram for a set of sample data. The intent is to use the sample data to perform a hypothesis test for the mean of the population from which the data were obtained. In each case, consult the graphs provided to decide whether to use the z-test, the t-test, or neither. Explain your answer.
a. The normal probability plot and histogram of the data are depicted in Fig. 9.49 on the next page; σ is known.
b. The normal probability plot and stem-and-leaf diagram of the data are depicted in Fig. 9.50 on the next page; σ is unknown?
FIGURE 9.50 Normal probability plot and stem-and-leaf diagram for Problem 35

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