Uniform Density Curves — Unit test Answers

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Heights of four-year-olds are Normally distributed, with a mean of 40 inches and a standard deviation of 3 inches. At his four-year checkup, Marlon’s height is measured as taller than 70% of boys his age. How tall is Marlon?Find the z-table here.

A
38.4 inches
B
41.6 inches
C
42.5 inches
D
43.8 inches
2
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Scores on a national English test are Normally distributed, with a mean score of 510 and a standard deviation of 75. Jaxon’s test score is in the 85th percentile. What is his test score, rounded to the nearest whole number?Find the z-table here.

A
549
B
561
C
573
D
588
3

The times for running a 5K for a local charity event are Normally distributed, with a mean time of 28 minutes and standard deviation of 5.4 minutes. Which time represents the 60th percentile?Find the z-table here.

A
19.6 minutes
B
26.6 minutes
C
29.4 minutes
D
36.4 minutes
4

Heights of four-year olds are Normally distributed, with a mean of 40 inches and a standard deviation of 3 inches. At her four-year checkup, Hannah's height measures in the 99th percentile. How tall is Hannah?Find the z-table here.

A
33.0 inches
B
34.1 inches
C
47.0 inches
D
48.2 inches
5

Scores on a national English test are Normally distributed, with a mean score of 510 and a standard deviation of 75. Sixty-eight percent of English tests were less than which score, rounded to the nearest whole number?Find the z-table here.

A
475
B
529
C
545
D
561
6

The salt content in snack bags of pretzels is Normally distributed, with a mean of 180 mg and a standard deviation of 15 mg. Eighty four percent of bags have a salt content higher than which value?Find the z-table here.

A
165.2 mg
B
179.2 mg
C
187.0 mg
D
194.9 mg
7

In a certain breed of cattle, the length of gestation has a mean of 284 days and a standard deviation is 5.5 days. What length of gestation, rounded to the nearest whole number, represents the 18th percentile?Find the z-table here.

A
279 days
B
282 days
C
285 days
D
289 days
9

In the standard Normal distribution, 43% of observations lie below which z-score?Find the z-table here.

A
–1.08
B
–0.18
C
0.18
D
1.08

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