Chapter 6: Q.13 (page 385)
What is the z-score of x= –, if it is standard deviations to the right of the mean?
Short Answer
Thescore will be
Chapter 6: Q.13 (page 385)
What is the z-score of x= –, if it is standard deviations to the right of the mean?
Thescore will be
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About what percent of values lie between the mean and one standard deviation?
Is X~N() a standardized normal distribution? Why or why not?
Two thousand students took an exam. The scores on the exam have an approximate normal distribution with a mean points and standard deviation points.
a. Calculate the first- and third-quartile scores for this exam.
b. The middle of the exam scores are between what two values?
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?
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