8.42 Travelbyus is an Internet-based travel agency wherein customers can see videos of the cities they plan to visit. The number of hits daily is a normally distributed random variable with a mean of 10,000 and a standard deviation of 2,400. a. What is the probability of getting more than 12,000 hits? b. What is the probability of getting fewer than 9,000 hits?

13.50 You wish to determine whether MBA graduates who majored in finance attract higher starting salaries than MBA graduates who majored in marketing. a. Describe a data-gathering process that produces observational data. b. Describe a data-gathering process that produces experimental data. c. If observational data indicate that finance majors attract higher salaries than do marketing majors, provide two explanations for this result. 

15.48 A random sample of 50 observations yielded the following frequencies for the standardized intervals: Interval Frequency Z ≤ -1 6 -1 < Z ≤ 0 27 0 < Z ≤ 1 14 Z < 1 3 Can we infer that the data are not normal? (Use α = .10.)