The tread life of a particular brand of tire is a random variable best described by a normal distribution with a mean of 60,000 miles and a standard deviation of 1500 miles.
What is the probability a certain tire of this brand will last between 56,850 miles and 57,300 miles? A) 0.0180 B) 0.9813 C) 0.4920 D) 0.4649
Q. 2A student scores 62 on a geography test and 261 on a mathematics test. The geography test has a mean of 80 and a standard deviation of 15. The mathematics test has a mean of 300 and a standard deviation of 26.
If the data for both tests are normally distributed, on which test did the student score better relative to the other students in each class? A) The student scored better on the geography test.
B) The student scored better on the mathematics test.
C) The student scored the same on both tests.
Q. 3To help consumers assess the risks they are taking, the Food and Drug Administration (FDA ) publishes the amount of nicotine found in all commercial brands of cigarettes. A new cigarette has recently been marketed.
The FDA tests on this cigarette gave a mean nicotine content of 28.5 milligrams and standard deviation of 2.2 milligrams for a sample of n = 9 cigarettes. The FDA claims that the mean nicotine content exceeds 31.2 milligrams for this brand of cigarette, and their stated reliability is 95. Do you agree? A) No, since the value 31.2 does not fall in the 95 confidence interval.
B) Yes, since the value 31.2 does fall in the 95 confidence interval.
C) Yes, since the value 31.2 does not fall in the 95 confidence interval.
D) No, since the value 31.2 does fall in the 95 confidence interval.
Q. 4If nothing is known about the shape of a distribution, what percentage of the observations fall within 2 standard deviations of the mean?
A) at least 75 B) at most 25
C) approximately 95 D) approximately 5
Q. 5Every fifth adult entering an airport is checked for extra security screening. What sampling technique is used?
A) systematic
B) simple random
C) cluster
D) convenience
E) stratified
Q. 6The tread life of a particular brand of tire is a random variable best described by a normal distribution with a mean of 60,000 miles and a standard deviation of 2800 miles.
What is the probability a particular tire of this brand will last longer than 57,200 miles? A) 0.8413 B) 0.1587 C) 0.2266 D) 0.7266
Q. 7A local bank needs information concerning the savings account balances of its customers. A random sample of 15 accounts was checked.
The mean balance was 686.75 with a standard deviation of 256.20. Find a 98
confidence interval for the true mean. Assume that the account balances are normally distributed. Round to the
nearest cent.
A) (513.17, 860.33 ) B) (238.23, 326.41 ) C) (326.21, 437.90 ) D) (487.31, 563.80 )
Q. 8Thirty-five math majors, 33 music majors and 45 history majors are randomly selected from 251 math majors, 518 music majors and 332 history majors at the state university. What sampling technique is used?
A) stratified
B) simple random
C) cluster
D) convenience
E) systematic
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