Chapter 6: Q.6 (page 385)
The value of
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The scores on a college entrance exam have an approximate normal distribution with mean, points and a standard deviation, points.
a. About of the values lie between what two values? These values are ________________. The -scores are ________________, respectively.
b. About of the values lie between what two values? These values are ________________. The -scores are ________________, respectively.
c. About of the values lie between what two values? These values are ________________. Thescores are ________________, respectively.
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?
Is equal to ? Why?
Using the information from Example 6.12, answer the following:
In , students took the SAT exam. The distribution of scores in the verbal section of the SAT had a mean and a standard deviation . Let X = a SAT exam verbal section score in . Then . Find the z-scores for and. Interpret each z-score. What can you say about and as they compare to their respective means and standard deviations ?
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