MATH200 — Practice Quiz: Chapter 7 — 20 min
Practice Quiz: Chapter 7
Work this like a regular quiz, using only your crib
yourself a maximum of 20 minutes,
then turn to the
solutions and see how
Be sure to
sketch and label your curve on appropriate problems.
Round probabilities to four decimal places.
Remember, you must show your work for full credit on any
problems involving computation.
1(points: 3½) Suppose that the new Ford Behemoth SUV gets a mean of
6.20 miles to the gallon, normally distributed with standard
deviation 0.90 mpg. Jane, who has taken a statistics
class, found that 85% of Ford
Behemoths get better gas mileage than hers does. What is her car’s
gas mileage, to two decimal places?
2(points: 1) What is the percentile rank of Jane’s car?
3(points: 3½) The times to assemble a particular product part are
normally distributed with a mean of 47.5 minutes and a standard
deviation of 8.5 minutes. What percent of assembly workers require
more than 60 minutes?
4(points: 1½) The standard normal curve is plotted in terms
of _____ (write in “z” or “x”).
It has a mean of _____ and a standard
deviation of ___.
5(points: 3) The lifetimes of Everlast AA batteries are normally
distributed. Between x=28.2 and x=34.1 hours, the area under the curve is
0.0742. Give two interpretations of this fact, in English.
(points: 2½) Fourteen rats were sent into space, and on their return to
Earth their red-blood-cell masses were measured. Here are the
data, in milliliters:
8.59 6.87 7.00
6.39 7.43 9.79 9.30
8.64 7.89 8.80 7.54
7.21 6.85 8.03
Are those figures normally distributed? Support your answer,
but you need not draw a graph.
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Solutions to this practice quiz are available at