QNT 561 FINAL EXAM – QUESTION AND
ANSWERS
1
A market researcher is interested in determining the average income for families in San Mateo County,
California. To accomplish this, she takes a random sample of 300 families from the county and uses the
data gathered from them to estimate the average income for families of the entire county. This process is
an example of _______.
inferential statistics
2
If x is a binomial random variable with n=10 and p=0.8, what is the probability that x is equal to
4?
.0055
question 3
The number of bags arriving on the baggage claim conveyor belt in a 3 minute time period
would best be modeled with the _________.
Poisson distribution
4
According to the central limit theorem, for samples of size 64 drawn from a population with µ = 800 and
σ = 56, the standard deviation of the sampling distribution of sample means would equal _______.
800
5
Suppose a population has a mean of 400 and a standard deviation of 24. If a random sample of size 144
is drawn from the population, the probability of drawing a sample with a mean less than 402 is _______.
0.8413
6
If x is a binomial random variable with n=10 and p=0.8, the mean value of x is _____.
, 8
7
According to the central limit theorem, for samples of size 64 drawn from a population with µ = 800 and
σ = 56, the mean of the sampling distribution of sample means would equal _______.
800
8
Completion time (from start to finish) of a building remodeling project is normally distributed
with a mean of 200 work-days and a standard deviation of 10 work-days. To be 99% sure that
we will not be late in completing the project, we should request a completion time of _______
work-days.
223
9
A researcher wants to determine the sample size necessary to adequately conduct a study to estimate the
population mean to within 5 points. The standard deviation of population values is 80 and the researcher
plans to use a 90% level of confidence. The sample size should be at least _______.
44
10
The expected (mean) life of a particular type of light bulb is 1,000 hours with a standard
deviation of 50 hours. The life of this bulb is normally distributed. What is the probability that
a randomly selected bulb would last fewer than 940 hours?
0.1151
11
A large national company is considering negotiating cellular phone rates for its employees. The Human
Resource department would like to estimate the proportion of its employee population who own an
Apple iPhone. A random sample of size 250 is taken and 40% of the sample own and iPhone.. The 95%
confidence interval to estimate the population proportion is _______.
ANSWERS
1
A market researcher is interested in determining the average income for families in San Mateo County,
California. To accomplish this, she takes a random sample of 300 families from the county and uses the
data gathered from them to estimate the average income for families of the entire county. This process is
an example of _______.
inferential statistics
2
If x is a binomial random variable with n=10 and p=0.8, what is the probability that x is equal to
4?
.0055
question 3
The number of bags arriving on the baggage claim conveyor belt in a 3 minute time period
would best be modeled with the _________.
Poisson distribution
4
According to the central limit theorem, for samples of size 64 drawn from a population with µ = 800 and
σ = 56, the standard deviation of the sampling distribution of sample means would equal _______.
800
5
Suppose a population has a mean of 400 and a standard deviation of 24. If a random sample of size 144
is drawn from the population, the probability of drawing a sample with a mean less than 402 is _______.
0.8413
6
If x is a binomial random variable with n=10 and p=0.8, the mean value of x is _____.
, 8
7
According to the central limit theorem, for samples of size 64 drawn from a population with µ = 800 and
σ = 56, the mean of the sampling distribution of sample means would equal _______.
800
8
Completion time (from start to finish) of a building remodeling project is normally distributed
with a mean of 200 work-days and a standard deviation of 10 work-days. To be 99% sure that
we will not be late in completing the project, we should request a completion time of _______
work-days.
223
9
A researcher wants to determine the sample size necessary to adequately conduct a study to estimate the
population mean to within 5 points. The standard deviation of population values is 80 and the researcher
plans to use a 90% level of confidence. The sample size should be at least _______.
44
10
The expected (mean) life of a particular type of light bulb is 1,000 hours with a standard
deviation of 50 hours. The life of this bulb is normally distributed. What is the probability that
a randomly selected bulb would last fewer than 940 hours?
0.1151
11
A large national company is considering negotiating cellular phone rates for its employees. The Human
Resource department would like to estimate the proportion of its employee population who own an
Apple iPhone. A random sample of size 250 is taken and 40% of the sample own and iPhone.. The 95%
confidence interval to estimate the population proportion is _______.
