STAT 201 Exam 2, Spring 2001

3O iaavte ew litte > Saading Room Time: 1| hr. 12/5/01 Math 207 Second Semester, 00-01 QUIZ I 1. A simple random sample of 50 items resulted in a sample mean of 32 and a sample standard deviation of 6. a) Compute the 90% confidence interval for the population mean. b) What is the margin of error? What does it mean with regards to the accuracy of the estimate 2. A sample of 250 factory workers in a certain city were found to have mean annual income of $24,000.The population standard deviation is known to be &= $5000. Compute the 99% confidence interval for the population mean. 3.The final grades in a course are normally distributed with a mean of 68 and a standard deviation 10. a) Find the 90" percentile grade in this distribution. b) Find the percentage of grades below a grade of 60. 4.In a population of 3000 people, 1470 were classified as blood type O, 1140 as type A, 300 as type B, and the remaining as type AB. Let the random variable x = 0,1,2, or 3 if a person’s blood type is O, A, B, or AB, respectively. Find the probability distribution for x. 5.The Webster National Bank has found that the average daily balance on personal checking accounts is $550.00, with a standard deviation of $150.00. In addition, the average daily balances have been found to be normally distributed. a) What percentage of personal checking account customers carry average daily balances in excess of $800.00? b) What percentage of the bank’s customers carry average daily balances between $300.00 and $700.00? 6. According to a survey in a certain year, the mean annual starting salary for accounting graduater is $26,542 and the standard deviationof those salaries is $2000. What is the probability that a simple. random sample of 100 accounting graduates will have a sample mean within $250 of the population mean?