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Chapter 6: Q.14 (page 385)
What is the z-score of x= , if it is standard deviations to the left of the mean?
The score is
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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 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
b.
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 children spend over ten hours per day unsupervised?
e. Seventy percent of the children spend at least how long per day unsupervised?
Suppose a normal distribution has a mean of six and a standard deviation of 1.5. What is the z-score of x = 5.5?
In a normal distribution, x = 5 and z = –1.25. This tells you that x = 5 is ____ standard deviations to the ____ (right or left) of the mean.
Is X~N() a standardized normal distribution? Why or why not?
The golf scores for a school team were normally distributed with a mean of and a standard deviation of three. Find the probability that a randomly selected golfer scored less than .
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