STAT 201 Final, Fall 2002

MERIO\S ONIVERSIT LIBRARY OF BEIROT Time: 2 hours STAT 201 Final Exam First Semester, 02-03 transformed so that they have a mean of 500 anda e GRE exam are t normally distributed. 1.Student scores on th standard deviation of 100. Furthermore, the scores are a) Find the quartiles for the GRE scores. b) Find the 99% percentile score. eople living in a town have a distribution that is skewed to the right with a a standard deviation of 10.9 kg. ght of a random sample of x and comment on 2. The weights of all p mean of 60.5 kg. and a) Let x be the mean wel Find the mean and standard deviation distribution. Explain. b) Find the probability that x is between 60 and 61kg. of 45 persons selected from this town. the shape of its sampling od workers employed by a large chain is 56. The standard deviation is $1.5. The hourly wages of the workers are normally distributed. a) Find the probability that a randomly selected fast-food worker for this chain has an hourly wage of $7 or more. b) £25 randomly selected workers for this chain are chosen, find the probability that their mean hourly w c) Why is the answer to part (b) reason. 3. The average hourly wage of fast-fo age is $7 or more. smaller than the answer to part (a)? Give a clear the taken from the same population, produced le means and standard deviations: Mean Standard Deviation 56.25 79 57.40 75 nt 90% confidence interval for the 4. Two samples of 100 observations each, following samp a) From the data of each sample, make a differe population mean Ht. 8. One of the confidence intervals found b) The true population mean is 55. n? Explain. contain 55.8. How could this happe' above doesn’t 5. Suppose, for a sample selected from a normally distributed distribution, x = 65.50 and s= 8.6. a) Construct a 95% confidence interval for 4s, assuming n= 16. b) Construct a 90% confidence interval for z:, assuming n= 16. c) Which of the intervals found in (a) or (b) gives a more precise estimate of p. Justify your answer. 6. A department store manager wishes to estimate at a 90% confidence level the mean amount spent by all customers at this store. From an earlier study, the manager knows that the standard deviation of amounts spent by customers at this store is $27. What sample size should he choose so that the estimate is within $3 of the population mean? (Assume that the amounts spent by customers at this store are normally distributed.) 7. A store manager wishes to find out whether there is a relation between ages of employees and the number of their absences a year. She used a random sample of 6 employees and collected the following data for the sample: Age % 418 26 39 48 53 58 Number of Absences Yf316 42 9 5 6 2 a) Calculate the linear correlation coefficient, r, for the data. b) Interpret the value of r, obtained in (a), in terms of the linear relationship between age and number of absences of the employees. Hint: Ex2= 10998, Zy? = 546. BERTON Tx este LIBRA Ry OF yEInUy