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Question 1 of 205.0 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. 1005C. 99.7%D. 95%Question 2 of 205.0 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. 62B. 63C. 63.5D. 64Question 3 of 205.0 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 120A. bB. b, cC. dD. a, bQuestion 4 of 205.0 PointsThe volumes of soda in quart soda bottles are normally distributed with a mean of 32.3 oz and a standard deviation of 1.2 oz. What is the probability that the volume of soda in a randomly selected bottle will be less than 32 oz?A. 0.5012B. 0.5010C. 0.4015D. 0.4013Question 5 of 205.0 PointsThe annual precipitation for one city is normally distributed with a mean of 28 inches and a standard deviation of 3.4 inches. Fill in the blanks.In 95% of the years, the precipitation in this city is between __________ and __________ inches.Apply the 68-95-99.7 rule to this question.A. 21.2, 34.8B. 21.2, 34.6C. 22.4, 34.6D. 22.4, 34.8Question 6 of 205.0 PointsIf light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, approximately what percentage of light bulbs has a life of more than 3000 hours?A. About 84%B. About 68%C. About 32%D. About 16%Question 7 of 205.0 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, cB. b, cC. a, bD. aQuestion 8 of 205.0 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, 152.4B. 121.6, 150.4C. 123.6, 150.4D. 122.6, 148.4Question 9 of 205.0 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. 123B. 118C. 112D. 111Question 10 of 205.0 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 11 of 205.0 PointsThe scores on a certain test are normally distributed with a mean score of 58 and a standard deviation of 4. What is the likelihood that a sample of 90 students will have a mean score of at least 58.4216?A. 0.8413B. 0.3413C. 0.3174D. 0.1587Question 12 of 205.0 PointsThe weights of the fish in a certain lake are normally distributed with a mean of 20 lb and a standard deviation of 6. If 9 fish are randomly selected, what is the likelihood that the mean weight will be between 17.6 and 21.6 lb?A. 0.9370B. 0.6800C. 0.6730D. 0.0968Question 13 of 205.0 PointsThe annual precipitation amounts in a certain mountain range are normally distributed with a mean of 88 inches, and a standard deviation of 10 inches. What is the likelihood that the mean annual precipitation during 25 randomly picked years will be less than 90.8 inches?A. 0.4192B. 0.5808C. 0.0808D. 0.9192Question 14 of 205.0 PointsThe amount of Jen’s monthly electric bill is normally distributed with a mean of $160 and a standard deviation of $14. Fill in the blanks.95% of her electric bills are between __________ and __________.Apply the 68-95-99.7 rule to this question.A. $140, $190B. $132, $190C. $140, $188D. $132, $188Question 15 of 205.0 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 $46.30B. About $43.30C. About $43.40D. about $43.20Question 16 of 205.0 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%Question 17 of 205.0 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, bB. b, dC. a, cD. aQuestion 18 of 205.0 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 19 of 205.0 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. 0.2416B. 0.2418C. 0.2417D. 0.2420Question 20 of 205.0 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. 3.53B. 3.42C. 3.23D. 3.13
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