Author:
Christine Farr

Assume the speed of vehicles along a stretch of I-10 has anapproximately normal distribution with a mean of 71 mph and astandard deviation of 8 mph.a.b.What proportion of the vehicles would be going less than 50mph?c.A new speed limit will be initiated such that approximately 10%of vehicles will be over the speed limit. What is the new speedlimit based on this criterion?d.11.The current speed limit is 65 mph. What is the proportion ofvehicles less than or equal to the speed limit?In what way do you think the actual distribution of speeds differsfrom a normal distribution?A group of students at a school takes a history test. The distribution isnormal with a mean of 25, and a standard deviation of 4.(a)(b)60.Everyone who scores in the top 30% of the distribution gets acertificate. What is the lowest score someone can get and stillearn a certificate?The top 5% of the scores get to compete in a statewide historycontest. What is the lowest score someone can get and still goonto compete with the rest of the state?The patient recovery time from a particular surgical procedure isnormally distributed with a mean of 5.3 days and a standard deviationof 2.1 days.What is the median recovery time?a.b.c.d.66.2.75.37.42.1Height and weight are two measurements used to track a child’sdevelopment. The World Health Organization measures childdevelopment by comparing the weights of children who are the sameheight and the same gender. In 2009, weights for all 80 cm girls in thereference population had a mean µ = 10.2 kg and standard deviationσ = 0.8 kg. Weights are normally distributed. X~ N(10.2, 0.8).Calculate the z-scores that correspond to the following weights andinterpret them.a.b.c.76.Suppose that the distance of fly balls hit to the outfield (in baseball) isnormally distributed with a mean of 250 feet and a standard deviationof 50 feet.a.b.c.62.b.c.If X = average distance in feet for 49 fly balls, then X ~_____(___, ____)What is the probability that the 49 fly balls traveled an averageof less than 240 feet? Sketch the graph. Scale the horizontalaxis X . Shade the region corresponding to the probability.Find the probability.Find the 80th percentile of the distribution of the average of 49 flyballs.Which of the following is NOT TRUE about the distribution for averages?a.b.c.d.96.If X = distance in feet for a fly ball, then X ~ _____(___, ____)If one fly ball is randomly chosen from this distribution, what isthe probability that this ball traveled fewer than 220 feet?Sketch the graph. Scale the horizontal axis X. Shade the regioncorresponding to the probability. Find the probability.Find the 80th percentile of the distribution of fly balls. Sketch thegraph, and write the probability statement.Suppose that the distance of fly balls hit to the outfield (in baseball) isnormally distributed with a mean of 250 feet and a standard deviationof 50 feet. We randomly sample 49 fly balls.a.70.11 kg7.9 kg12.2 kg

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