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Chapter 7: Q .31 (page 429)
What is the z-score for Σx = 840?
The z-score for Σx = 840 is approximately 26
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What three things must you know about distribution to find the probability of sums?
Yoonie is a personnel manager in a large corporation. Each month she must review of the employees. From past experience, she has found that the reviews take her approximately four hours each to do with a population standard deviation of hours. Let Χ be the random variable representing the time it takes her to complete one review. Assume Χ is normally distributed. Let be the random variable representing the meantime to complete the reviews. Assume that the reviews represent a random set of reviews.
Find the th percentile for the meantime to complete one month's reviews. Sketch the graph.
a.
b. The th Percentile =____________
Four friends, Janice, Barbara, Kathy and Roberta, decided to carpool together to get to school. Each day the driver would be chosen by randomly selecting one of the four names. They carpool to school for days. Use the normal approximation to the binomial to calculate the following probabilities. Round the standard deviation to four decimal places.
a. Find the probability that Janice is the driver at mostdays.
b. Find the probability that Roberta is the driver more than days.
c. Find the probability that Barbara drives exactly of those days.
Suppose that the duration of a particular type of criminal trial is known to have a mean of days and a standard deviation of seven days. We randomly sample nine trials.
a. In words,
b.
c. Find the probability that the total length of the nine trials is at least days.
d. Ninety percent of the total of nine of these types of trials will last at least how long?
According to Boeing data, the airliner carriespassengers and has doors with a height of inches. Assume for a certain population of men we have a mean height of inches and a standard deviation of inches.
a. What doorway height would allow of men to enter the aircraft without bending?
b. Assume that half of the passengers are men. What mean doorway height satisfies the condition that there is a probability that this height is greater than the mean height ofmen?
c. For engineers designing the , which result is more relevant: the height from part a or part b? Why?
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