MATH 227 STATISTICS FINAL EXAM - West Los Angeles College

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55. The diameter of ball bearings produced in a manufacturing process can be explained using a uniform distribution over the interval 3.5 to 5.5 millimeters. What is the probability that a randomly selected ball bearing has a diameter greater than 4 millimeters Hint: Draw the distribution, shade appropriate area. a. .7272 b. .4444 c. .75 d. .50 56. For air travelers, one of the biggest complaints is of the waiting time between when the airplane taxis away from the terminal until the flight takes off. This waiting time is known to have a skewed right distribution with a mean of 10 minutes and a standard deviation of 8 minutes. Suppose 100 flights have randomly been sampled. Describe the sampling distribution of the mean waiting time between when the airplane taxis away from the terminal until the flight takes off for these 100 flights. a. Distribution skewed right, Mean = 10 minutes, standard deviation = .8 minutes b. Distribution skewed right, Mean = 10 minutes, standard deviation = 8 minutes c. Distribution normal, Mean = 10 minutes, standard deviation = 8 minutes d. Distribution normal, Mean = 10 minutes, standard deviation = .8 minutes 57. Which of the following statements about the sampling distribution of x is incorrect a. The sampling distribution is approximately normal whenever the sample size is sufficiently large (n > 30). b. The sampling distribution is generated by repeatedly taking samples of size n and computing the sample means. c. The mean of the sampling distribution is µ x . d. The standard deviation of the sampling distribution is σ x . 58. The average score of all pro golfers for a particular course has a mean of 70 and a standard deviation of 3.0. Suppose 36 golfers played the course today. Find the probability that the average score of the 36 golfers exceeded 71. Hint: This is P ( x > 71) . a. .1293 b. .4772 c. .3707 d. .0228 59. If we repeatedly sample from a population samples of size n, and calculate the sample median for each sample, the accumulation of these sample medians would result in a. a confidence interval for the population variation b. the sampling distribution for the population mean c. an estimate of the sample median d. the sampling distribution of the sample median 8
60. In the construction of confidence intervals, if all other quantities are unchanged, an increase in the sample size will lead to a _________ interval. a. narrower b. wider c. less significant d. biased 61. It is desired to estimate which of the two soft drinks, Coke or Pepsi, West Los Angeles College students prefer. A random sample of 167 students produced the following 95% confidence interval for the proportion of students who prefer Pepsi: (.344, .494). Identify the point estimate for estimating the true proportion of West Los Angeles College students who prefer Pepsi. a. .494 b. 1.96 c. 0.95 d. .344 e. .419 62. Which of the calculated values of a test statistic would have the smallest p-value for an upper tailed test a. t = 3.05 with 10 degrees of freedom b. t = 3.05 with 20 degrees of freedom c. z = 3.05 d. z = 1.46 63. In a two-tailed large sample test with calculated test statistic z = 1.68, the p-value is a. .0930 b. .0465 c. .9170 d. .9535 64. The probability that a normal variable X falls within 2 standard deviations of the mean is a. .0228 b. .9772 c. .0456 d. .9544 9
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MATH 227 STATISTICS FINAL EXAM - West Los Angeles College

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