20. The student body of a large university consists of 60% female
students. A random sample of 8 students is selected. What is the
probability that among the students in the sample at least 7 are female?
a. 0.1064
b. 0.0896
c. 0.0168
d. 0.8936
23. Forty percent of all registered voters in a national election are
female. A random sample of 5 voters is selected. The probability that
the sample contains 2 female voters is
a. 0.0778
b. 0.7780
c. 0.5000
d. 0.3456
30. Given that Z is a standard normal random variable, what is the value
of Z if the are to the left of Z is 0.0559?
a. 0.4441
b. 1.59
c. 0.0000
d. 1.50
36. A sample of 400 observations will be taken from an infinite
population. The population proportion equals 0.8. The probability that
the sample proportion will be greater than 0.83 is
a. 0.4332
b. 0.9332
c. 0.0668
d. 0.5668
37. In order to determine an interval for the mean of a population with
unknown standard deviation a sample of 25 items is selected. The mean of
the sample is determined to be 23. The number of degrees of freedom for
reading the t value is
a. 22
b. 23
c. 24
d. 25
Exhibit 8-1
In order to estimate the average time spent on the computer terminals
per student at a local university, data were collected for a sample of
81 business students over a one week period. Assume the population
standard deviation is 1.2 hours.
39. Refer to Exhibit 8-1. With a 0.95 probability, the margin of error
is approximately
a. 0.26
b. 1.96
c. 0.21
d. 1.64
40. Refer to Exhibit 8-1. If the sample mean is 9 hours, then the 95%
confidence interval is
a. 7.04 to 110.96 hours
b. 7.36 to 10.64 hours
c. 7.80 to 10.20 hours
d. 8.74 to 9.26 hours
41. A random sample of 100 people was taken. Eighty of the people in the
sample favored Candidate A. The 95% confidence interval for the true
proportion of people who favors Candidate A is
a. 0.722 to 0.878
b. 0.762 to 0.838
c. 78.04 to 81.96
d. 62.469 to 97.531
42. We are interested in conducting a study in order to determine what
percentage of voters of a state would vote for the incumbent governor.
What is the minimum size sample needed to estimate the population
proportion with a margin of error of 0.05 or less at 95% confidence?
a. 200
b. 100
c. 58
d. 196
4. Ten percent of the items produced by a machine are defective. Out of
15 items chosen at random,
a. what is the probability that exactly 3 items will be defective?
b. what is the probability that less than 3 items will be defective?
c. what is the probability that exactly 11 items will be non-defective?
Statistics Homework Solutions
#41182
Statistics Review: Probability; Standard Normal Random Variable; Population Standard Deviation; Confidence Interval etc.
20. The student body of a large university consists of 60% female students. A random sample of 8 students is selected. What is the probability that among the students in the sample at least 7 are female?
a. 0.1064
b. 0.0896
c. 0.0168
d. 0.8936
23. Forty percent of all registered voters in a national election are female. A random sample of 5 voters is selected. The probability that the sample contains 2 female voters is
a. 0.0778
b. 0.7780
c. 0.5000
d. 0.3456
30. Given that Z is a standard normal random variable, what is the value of Z if the are to the left of Z is 0.0559?
a. 0.4441
b. 1.59
c. 0.0000
d. 1.50
36. A sample of 400 observations will be taken from an infinite population. The population proportion equals 0.8. The probability that the sample proportion will be greater than 0.83 is
a. 0.4332
b. 0.9332
c. 0.0668
d. 0.5668
37. In order to determine an interval for the mean of a population with unknown standard deviation a sample of 25 items is selected. The mean of the sample is determined to be 23. The number of degrees of freedom for reading the t value is
a. 22
b. 23
c. 24
d. 25
Exhibit 8-1
In order to estimate the average time spent on the computer terminals per student at a local university, data were collected for a sample of 81 business students over a one week period. Assume the population standard deviation is 1.2 hours.
39. Refer to Exhibit 8-1. With a 0.95 probability, the margin of error is approximately
a. 0.26
b. 1.96
c. 0.21
d. 1.64
40. Refer to Exhibit 8-1. If the sample mean is 9 hours, then the 95% confidence interval is
a. 7.04 to 110.96 hours
b. 7.36 to 10.64 hours
c. 7.80 to 10.20 hours
d. 8.74 to 9.26 hours
41. A random sample of 100 people was taken. Eighty of the people in the sample favored Candidate A. The 95% confidence interval for the true proportion of people who favors Candidate A is
a. 0.722 to 0.878
b. 0.762 to 0.838
c. 78.04 to 81.96
d. 62.469 to 97.531
42. We are interested in conducting a study in order to determine what percentage of voters of a state would vote for the incumbent governor. What is the minimum size sample needed to estimate the population proportion with a margin of error of 0.05 or less at 95% confidence?
a. 200
b. 100
c. 58
d. 196
4. Ten percent of the items produced by a machine are defective. Out of 15 items chosen at random,
a. what is the probability that exactly 3 items will be defective?
b. what is the probability that less than 3 items will be defective?
c. what is the probability that exactly 11 items will be non-defective?
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