QNT 561 FINAL EXAM 1 – QUESTION AND ANSWERS

QNT 561 FINAL EXAM 1 – QUESTION AND ANSWERS 1. According to the central limit theorem, for samples of size 64 drawn from a population with µ = 800 and σ = 56, the mean of the sampling distribution of sample means would equal _______. a. 800 2. The empirical rule says that approximately what percentage of the values would be within 2 standard deviations of the mean in a bell shaped set of data? a. 95% 3. Ophelia O'Brien, VP of Consumer Credit of American First Banks (AFB), monitors the default rate on personal loans at the AFB member banks. One of her standards is "no more than 5% of personal loans should be in default." On each Friday, the default rate is calculated for a sample of 500 personal loans. Last Friday's sample contained 30 defaulted loans. Ophelia's null hypothesis is _______. a. P = 0.05 4. According to the central limit theorem, for samples of size 64 drawn from a population with µ = 800 and σ = 56, the standard deviation of the sampling distribution of sample means would equal _______. a. 7 5. The mean life of a particular brand of light bulb is 1200 hours and the standard deviation is 75 hours. Tests show that the life of the bulb is approximately normally distributed. It can be concluded that approximately 68% of the bulbs will last between _______. a. hours 6. A researcher wants to determine the sample size necessary to adequately conduct a study to estimate the population mean to within 5 points. The standard deviation of population values is 80 and the researcher plans to use a 90% level of confidence. The sample size should be at least _______. a. 693 7. If x is a binomial random variable with n=10 and p=0.8, the mean value of x is _____. a. 8 8. The mean life of a particular brand of light bulb is 1200 hours. If you know that at about 95% of this brand of bulbs will last between 1100 and 1300 hours, then what is the standard deviation of the light bulbs’ life? a. 50 9. Life tests performed on a sample of 13 batteries of a new model indicated: (1) an average life of 75 months, and (2) a standard deviation of 5 months. Other battery models, produced by similar processes, have normally distributed life spans. The 98% confidence interval for the population mean life of the new model is _________. a. 71.28 to 78.72 10. A large industrial firm allows a discount on any invoice that is paid within 30 days. Of all invoices, 10% receive the discount. In a company audit, 10 invoices are sampled at random. The probability that fewer than 3 of the 10 sampled invoices receive the discount is approximately_______________. a. 0.9298