Download STA220-Exam 3 Name: Multiple Choice worth 3 points each The

STA220-Exam 3
Name: _______________________
Multiple Choice worth 3 points each
1. The owner of Get-A-Away Travel has recently surveyed a random sample of 496 customers to
determine whether the mean age of the agency's customers is over 24. The appropriate hypotheses
are 𝐻𝑜 : 𝜇 = 24, 𝐻𝑎 : 𝜇 > 24. If he concludes the mean age is over 24 when it is not, he makes a
__________ error. If he concludes the mean age is not over 24 when it is, he makes a
__________ .
A) Type I; Type II
B) Type I; Type I
C) Type II; Type II
D) Type II; Type I
2. If a hypothesis test were conducted using α = 0.05, to which of the following p-values would
cause the null hypothesis to be rejected.
A) 0.100
B) 0.040
C) 0.055
D) 0.060
3. A ______________ is a statement or claim regarding a characteristic of one or more populations.
A) hypothesis
B) conclusion
C) conjecture
D) fact
4. Determine the critical value for a right-tailed test of a population mean at the α = 0.001 level of
significance with 15 degrees of freedom.
A) 3.733
B) 2.602
C) -3.733
5. Which of the following is not a characteristic of Studentsʹ t-distribution?
A)
B)
C)
D)
mean of 1
symmetric distribution
depends on degrees of freedom
For large samples, the t and z distributions are nearly equivalent.
D) 3.787
6. (8 points) A 1993 study of in-state annual tuition rates at public schools in the US drew a random
sample of 56 public colleges and universities that had a mean of $2,319 and a standard deviation
of $1,136. Construct the 95% confidence interval for the true mean annual, in-state tuition costs
for US colleges and universities in 1993. In an interview from 1993, a college president claimed
the $3,527 per year in-state tuition that his college charged was average for public schools. Does
the interval you created contradict his claim? (Show all work and round to 3 decimal places.)
7. (8 points) A sample of 28 healthy babies has an average birth weight of 6.83 lbs and a standard
deviation of 1.53 lbs. Construct a 95% confidence interval for the true average weight for healthy
babies. If another study revealed that babies exposed to cocaine prenatally had an average birth
weight of 4.92 lbs, does it seem that cocaine might lead to lower than normal birth weights?
(Show all work and round to 3 decimal places.)
8. (8 points) A college freshman wants to estimate the true time it takes to have his order completed
at the Subway sandwich shop on campus. He has estimated that the standard deviation for
ordercompletion times is 3.3 minutes. If he wants to estimate the true average, order-completion
time to within one minute using a 95% confidence interval, how many times will he have to time
himself purchasing a sandwich at Subway?
9.
(8 points) The Natural Foods Diet claims that people lose an average of ten pounds in two months
on the plan. A random sample of 26 people lost an average 8.9 pounds on the diet in two months.
The standard deviation was 3.25 pounds. Use a 2% significance level to test the claim that the
diet helps people lose an average of 10 pounds in two months.
a. Set up the hypotheses test.
b. Make the appropriate conclusion.
10. (8 points) A professor claims that at most 10% of the class gets A’s each semester in his course. A
random sample of 100 students from previous terms show that he gave out 15 A’s. Using a 5%
significance level, test the professor’s claim.
a. Set up the hypotheses test.
b. Make the appropriate conclusion.
11. (8 points) A doctor claims that the average woman is not more than 63 inches tall. A biologist
disagrees. A sample of 47 women has a mean of 64.1 inches and a standard deviation of 2.3
inches. State the null and alternative hypotheses necessary to test the doctor's claim. If we were to
decide to reject the null hypothesis, how would we state the final conclusion?
a. Set up the hypotheses test.
b. Make the appropriate conclusion.
12. (2 point each) True or False
(a) The null hypothesis represents the status quo to the party performing the sampling experiment.
A) True
B) False
(b) A Type I error occurs when we accept a false null hypothesis.
A) True
B) False
(c) The smaller the p-value in a test of hypothesis, the more significant the results are.
A) True
B) False
(d) As the sample size gets larger, the standard error of the sampling distribution of the sample mean gets
larger as well.
A) True
B) False