Posted: September 19th, 2022

ASHWORTH MA260 ONLINE EXAM 4

Question 1 of 205.0/ 5.0 PointsAt one college, GPA’s are normally distributed with a mean of 2.9 and a standard deviation of 0.6. Find the 70th percentile. A. 3.53 B. 3.42 C. 3.23 D. 3.13Question 2 of 205.0/ 5.0 PointsThe lifetimes of projector bulbs of a particular type are normally distributed with a mean of 470 hours and a standard deviation of 15 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean on either side?Apply the 68-95-99.7 rule to this question. A. 68% B. 99.7% C. 95% D. 100%Question 3 of 205.0/ 5.0 PointsThe amount of Jen’s monthly phone bill is normally distributed with a mean of $50 and a standard deviation of $10. Find the 25th percentile. A. About $46.30 B. About $43.30 C. About $43.40 D. about $43.20Question 4 of 205.0/ 5.0 PointsThe mean score on the exit examination for an urban high school is 63 with a standard deviation of 8. What is the mean of the distribution of sample means with a sample size of 9? A. 62 B. 63 C. 63.5 D. 64Question 5 of 205.0/ 5.0 PointsThe diameters of pencils produced by a certain machine are normally distributed with a mean of 0.30 inches and a standard deviation of 0.01 inches. In a random sample of 460 pencils, approximately how many would you expect to have a diameter less than 0.293 inches? A. 123 B. 118 C. 112 D. 111Question 6 of 205.0/ 5.0 PointsDecide which of the described variables likely have a normal or near-normal distribution.1. The number of credits remaining until graduation for the students in a small liberal arts college2. The heights of male students in an advanced placement mathematics class3. The number of sixes showing when two dice are rolled A. a B. b C. c D. NoneQuestion 7 of 205.0/ 5.0 PointsThe systolic blood pressures of the patients at a hospital are normally distributed with a mean of 136 mm Hg and a standard deviation of 12 mm Hg. Find the two blood pressures having these properties: the mean is midway between them and 76.98% of all blood pressures are between them. A. 121.6, 152.4 B. 121.6, 150.4 C. 123.6, 150.4 D. 122.6, 148.4Question 8 of 205.0/ 5.0 PointsWhich of the following statements concerning the standard normal curve is/are true (if any)?a) The area under the standard normal curve to the left of -3 is zero.b) The area under the standard normal curve between any two z-scores is greater than zero.c) The area under the standard normal curve between two z-scores will be negative if both z-scores are negative.d) The area under the standard normal curve to the left of any z-score is less than 1. A. a, b B. b, d C. a, c D. aQuestion 9 of 205.0/ 5.0 PointsWhich of the following statements concerning areas under the standard normal curve is/are true?a) If a z-score is negative, the area to its right is greater than 0.5.b) If the area to the right of a z-score is less than 0.5, the z-score is negative.c) If a z-score is positive, the area to its left is less than 0.5. A. a, c B. b, c C. a, b D. aQuestion 10 of 205.0/ 5.0 PointsThe mean score on the exit examination for an urban high school is 63 with a standard deviation of 9. What is the standard deviation of the distribution of sample means with a sample size of 9? A. 2 B. 3 C. 4 D. 4.1Question 11 of 200.0/ 5.0 PointsA study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 Chevrolet Cavalier shows that the mean is 8.4 hours and the standard deviation is 1.77 hours. Assume that a random sample of 40 mechanics is selected and the mean rebuild time of the sample is computed. Assuming the mean times are normally distributed, what percentage of sample means are greater than 7.7 hours? A. 0.62% B. 34.46% C. 65.54% D. 99.38%Question 12 of 205.0/ 5.0 PointsThe area under the standard normal curve between 1 and 2 is equal to 0.1359. Scores on a particular aptitude test are normally distributed with a mean of 100 and a standard deviation of 10. Which of the following are equal to 13.59%?a) The percentage of scores between 120 and 130b) The percentage of scores between 110 and 120c) The percentage of scores between 80 and 90d) The percentage of scores between 90 and 120 A. b B. b, c C. d D. a, bQuestion 13 of 200.0/ 5.0 PointsDecide which of the described variables is/are likely to have a normal or near-normal distribution.a) The heights of corn stalks in one row of corn that is half a mile longb) The numbers of viewers of each of the channels from 202 to 550 on Direct TV at 7:00 PM CDT on the third Thursday of November 2012 (349 data values) A. a B. b C. a and b D. neitherQuestion 14 of 205.0/ 5.0 PointsA bank’s loan officer rates applicants for credit. The ratings are normally distributed with a mean of 200 and a standard deviation of 50. If an applicant is randomly selected, find the probability of a rating that is between 225 and 275. A. 0.2416 B. 0.2418 C. 0.2417 D. 0.2420Question 15 of 205.0/ 5.0 PointsThe lifetimes of light bulbs of a particular type are normally distributed with a mean of 270 hours and a standard deviation of 11 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean on either side?Apply the 68-95-99.7 rule to this questions. A. 68% B. 1005 C. 99.7% D. 95%Question 16 of 200.0/ 5.0 PointsDecide which of the described variables likely have a normal or near-normal distribution.a) The amount of change held by a teacher at the end of each day for a yearb) The amount of pocket money held by each student at a mid-sized liberal arts college at a given timec) The number of heads that show when two coins are tossed A. a B. b C. c D. NoneQuestion 17 of 205.0/ 5.0 PointsIf light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours? A. About 25% B. About 50% C. About 75% D. About 68%Question 18 of 205.0/ 5.0 PointsIf light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, use the 68-95-99.7 rule to approximate the percentage of light bulbs having a life between 2000 hours and 3500 hours? A. About 13.5% B. About 50% C. About 68% D. About 81.5%Question 19 of 205.0/ 5.0 PointsA math teacher gives two different tests to measure students’ aptitude for math. Scores on the first test are normally distributed with a mean of 24 and a standard deviation of 4.5. Scores on the second test are normally distributed with a mean of 70 and a standard deviation of 11.3. Assume that the two tests use different scales to measure the same aptitude. If a student scores 29 on the first test, what would be his equivalent score on the second test? (That is, find the score that would put him in the same percentile.) A. 87 B. 85 C. 86 D. 83Question 20 of 205.0/ 5.0 PointsThe diameters of bolts produced by a certain machine are normally distributed with a mean of 0.25 inches and a standard deviation of 0.01 inches. What percentage of bolts will have a diameter greater than 0.24 inches? A. 79.13% B. 82.46% C. 84.13% D. 84.46%

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