Questions from Applied Statistics

Q: Of 43 bank customers depositing a check, 18 received some cash

Of 43 bank customers depositing a check, 18 received some cash back. (a) Construct a 90 percent confidence interval for the proportion of all depositors who ask for cash back. (b) Check the normality...

Q: A survey showed that 4.8 percent of the 250 Americans

A survey showed that 4.8 percent of the 250 Americans surveyed had suffered some kind of identity theft in the past 12 months. (a) Construct a 99 percent confidence interval for the true proportion of...

Q: A random survey of 500 students was conducted from a population of

A random survey of 500 students was conducted from a population of 2,300 students to estimate the proportion who had part-time jobs. The sample showed that 245 had part-time jobs. Calculate the 90 per...

Q: Last year, a study showed that the average ATM cash withdrawal

Last year, a study showed that the average ATM cash withdrawal took 65 seconds with a standard deviation of 10 seconds. The study is to be repeated this year. How large a sample would be needed to est...

Q: Popcorn kernels are believed to take between 100 and 200 seconds to

Popcorn kernels are believed to take between 100 and 200 seconds to pop in a certain microwave. (a) Estimate σ using Method 3 from Table 8.11. (b) What sample size (number of kernels) would...

Q: J.D. Power and Associates says that 60 percent of

J.D. Power and Associates says that 60 percent of car buyers now use the Internet for research and price comparisons. (a) Find the probability that in a sample of 8 car buyers, all 8 will use the Inte...

Q: Between 11 p.m. and midnight on Thursday night,

Between 11 p.m. and midnight on Thursday night, Mystery Pizza gets an average of 4.2 telephone orders per hour. Find the probability that (a) at least 30 minutes will elapse before the next telephone...

Q: Analysis showed that the mean arrival rate for vehicles at a certain

Analysis showed that the mean arrival rate for vehicles at a certain Shell station on Friday afternoon last year was 4.5 vehicles per minute. How large a sample would be needed to estimate this year’s...

Q: Noodles & Company wants to estimate the mean spending per customer at

Noodles & Company wants to estimate the mean spending per customer at a certain restaurant with 95 percent confidence and an error of ±$0.25. What is the required sample size, assuming a standard devi...

Q: In an intra-squad swim competition, men’s freestyle 100 swim

In an intra-squad swim competition, men’s freestyle 100 swim times at a certain university ranged from 43.89 seconds to 51.96 seconds. (a) Estimate the standard deviation using Method 3 (the Empirical...