STATISTICS 200 - ILLOWSKY CHAPTER 6 AND 7.
Use the following information to answer the next two exercises: The patient recovery time from a particular surgical
procedure is normally distributed with a mean of 5.3 days and a standard deviation of 2.1 days.
60. What is the median recovery time?
66. Height and weight are two measurements used to track a child’s development. TheWorld Health Organization measures
child development by comparing the weights of children who are the same height and the same gender. In 2009, weights for
all 80 cm girls in the reference population had a mean μ = 10.2 kg and standard deviation σ = 0.8 kg. Weights are normally
distributed. X ~ N(10.2, 0.8). Calculate the z-scores that correspond to the following weights and interpret them.
a. 11 kg
b. 7.9 kg
c. 12.2 kg
76. 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
c. Find the 80th percentile of the distribution of fly balls. Sketch the graph, and write the probability statement.
88. Facebook provides a variety of statistics on its Web site that detail the growth and popularity of the site.
On average, 28 percent of 18 to 34 year olds check their Facebook profiles before getting out of bed in the morning. Suppose
this percentage follows a normal distribution with a standard deviation of five percent.
a. Find the probability that the percent of 18 to 34-year-olds who check Facebook before getting out of bed in the
morning is at least 30.
b. Find the 95th percentile, and express it in a sentence.
62. 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. We randomly sample 49 fly balls.
a. If X ¯ = average distance in feet for 49 fly balls, then X ¯ ~ _______(_______,_______)
b. What is the probability that the 49 balls traveled an average of less than 240 feet? Sketch the graph. Scale the
horizontal axis for X ¯ . Shade the region corresponding to the probability. Find the probability.
c. Find the 80th percentile of the distribution of the average of 49 fly balls.
70. Which of the following is NOT TRUE about the distribution for averages?
a. The mean, median, and mode are equal.
b. The area under the curve is one.
c. The curve never touches the x-axis.
d. The curve is skewed to the right.
96. A typical adult has an average IQ score of 105 with a standard deviation of 20. If 20 randomly selected adults are given
an IQ tesst, what is the probability that the sample mean scores will be between 85 and 125 points?
|Due By (Pacific Time)||11/15/2015 12:00 am|
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