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Chapter 6: Q 17 (page 385)
Suppose X ~ N(9, 5). What value of x has a z-score of 鈥�0.5?
The value of is
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A \(\$1\) scratch off lotto ticket will be a winner one out of five times. Out of a shipment of \(n=190\) lotto tickets, find the probability for the lotto tickets that there are
a. somewhere between \(34\) and \(54\) prizes.
b. somewhere between \(54\) and \(64\) prizes.
c. more than \(64\) prizes.
About what percent of values lie between the first and second standard deviations from the mean (both sides)?
Suppose that the distance of fly balls hit to the outfield (in baseball) is normally distributed with a mean of 250 feet and a standard deviation of 50 feet.
a. If X = distance in feet for a fly ball, then X ~ _____(_____,_____)
b. If one fly ball is randomly chosen from this distribution, what is the probability that this ball traveled fewer than 220 feet? Sketch the graph. Scale the horizontal axis X. Shade the region corresponding to the probability. Find the probability.
c. Find the 80th percentile of the distribution of fly balls. Sketch the graph, and write the probability statement.
齿词狈(鈥�)
What is the median?
In China, four-year-olds average three hours a day unsupervised. Most of the unsupervised children live in rural areas, considered safe. Suppose that the standard deviation is 1.5 hours and the amount of time spent alone is normally distributed. We randomly select one Chinese four-year-old living in a rural area. We are interested in the amount of time the child spends alone per day.
a. In words, define the random variable X.
b. X ~ _____(_____,_____)
c. Find the probability that the child spends less than one hour per day unsupervised. Sketch the graph, and write the probability statement.
d. What percent of the children spend over ten hours per day unsupervised?
e. Seventy percent of the children spend at least how long per day unsupervised?
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