STAT 217 Questions with Correct Answers (Grade A+)
Question 1: Specify what Type II error (missed opportunity) represents in this situation. A Type II
error happens when you fail to reject the null hypothesis, but the null hypothesis was false.
A. The proportion of students who would read the paper is 0.10, but we decide it is more than 0.10.
B. The proportion of students who would read the paper is more than 0.10, but we do NOT find strong evidence
that it is more than 0.10.
Answer: B. The proportion of students who would read the paper is more than 0.10, but we do NOT find
strong evidence that it is more than 0.10.
Question 2: Specify what Type I error (false alarm) represents in this situation. A Type I error happens
when we reject the null hypothesis, but the null hypothesis was true.
A. The proportion of students who would read the paper is 0.10, but we decide it is more than 0.10.
B. The proportion of students who would read the paper is more than 0.10, but we do NOT find strong evidence
that it is more than 0.10.
Answer: A. The proportion of students who would read the paper is 0.10, but we decide it is more than 0.10.
Question 3: Describe what Type I error (false alarm) represents in this situation.
a. The patient had the disease, but the test says the patient is healthy.
b. The patient does not have the disease, but the test says the patient has the disease
Answer: B. The patient does not have the disease, but the test says the patient has the disease
Question 4: Describe what Type II error (missed opportunity) represents in this situation.
a. The patient does not have the disease, but the test says the patient has the disease.
b. The patient has the disease, but the test says the patient is healthy.
Answer: B. The patient has the disease, but the test says the patient is healthy.
Question 5: What type of error would you consider to be more serious (i.e. could lead to a more
disastrous outcome)?
a. Type I error
b. Type II error
Answer: B. Type II error
Question 6: When we say that 0.50 is a plausible value for a population proportion (parameter),
plausible means 0.50 will _________.
a. not be in the 95% confidence interval
b. be in the 95% confidence interval
Answer: B. be in the 95% confidence interval
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, Question 7: Suppose a 95% confidence interval is constructed from a sample proportion and 0.50 is
contained in the interval. Which of the following are true?
a. A 99% confidence interval constructed from the same sample proportion will definitely NOT contain 0.50.
b. A 99% confidence interval constructed from the same sample proportion will definitely contain 0.50.
c. A 90% confidence interval constructed from the same sample proportion will definitely NOT contain 0.50.
d. A 90% confidence interval constructed from the same sample proportion will definitely contain 0.50.
Answer: B. A 99% confidence interval constructed from the same sample proportion will definitely contain
0.50.
Question 8: What proportion of San Luis Obispo (SLO) residents dine at restaurants at least once a
week? To investigate, a local high school student, Deidre, decides to conduct a survey. She selects a
random sample of adult residents of SLO, asks each participant whether he/she dines at restaurants at
least once a week, and records their responses. Then, she uses her data to find a 95% confidence
interval for the proportion of SLO adults who dine out at least once a week to be (0.38, 0.44). The 99%
confidence interval based on the same data would be:
a. Wider, because to be more confident we need to widen the interval.
b. We need more information to answer this.
c. Narrower, because the more confident we are the narrower the interval.
Answer: A. Wider, because to be more confident we need to widen the interval.
Question 9: According to the 95% confidence interval:
a. There is not convincing evidence that less than half of SLO residents dine at restaurants at least once a week,
because the interval does not contain 0.50.
b. There is convincing evidence that less than half of SLO residents dine at restaurants at least once a week,
because the interval does not contain 0.50.
c. Neither of the other choices is correct.
Answer: B. There is convincing evidence that less than half of SLO residents dine at restaurants at least
once a week, because the interval does not contain 0.50.
Question 10: Based on an August 2013 Gallup poll, a 95% confidence interval for the proportion of
American adults that thought math was the most valuable subject they studied in school is 0.31 to 0.37.
Explain exactly what the confidence interval is estimating.
a. The confidence interval is estimating the proportion of all respondents to the poll that thought math was the
most valuable subject they studied in school.
b. The confidence interval is estimating the mean of all American adults that thought math was the most
valuable subject they studied in school.
c. The confidence interval is estimating the mean of all respondents to the poll that thought math was the most
valuable subject they studied in school.
d. The confidence interval is estimating the proportion of all American adults that thought math was the most
valuable subject they studied in school.
Answer: D. The confidence interval is estimating the proportion of all American adults that thought math
was the most valuable subject they studied in school.
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Question 1: Specify what Type II error (missed opportunity) represents in this situation. A Type II
error happens when you fail to reject the null hypothesis, but the null hypothesis was false.
A. The proportion of students who would read the paper is 0.10, but we decide it is more than 0.10.
B. The proportion of students who would read the paper is more than 0.10, but we do NOT find strong evidence
that it is more than 0.10.
Answer: B. The proportion of students who would read the paper is more than 0.10, but we do NOT find
strong evidence that it is more than 0.10.
Question 2: Specify what Type I error (false alarm) represents in this situation. A Type I error happens
when we reject the null hypothesis, but the null hypothesis was true.
A. The proportion of students who would read the paper is 0.10, but we decide it is more than 0.10.
B. The proportion of students who would read the paper is more than 0.10, but we do NOT find strong evidence
that it is more than 0.10.
Answer: A. The proportion of students who would read the paper is 0.10, but we decide it is more than 0.10.
Question 3: Describe what Type I error (false alarm) represents in this situation.
a. The patient had the disease, but the test says the patient is healthy.
b. The patient does not have the disease, but the test says the patient has the disease
Answer: B. The patient does not have the disease, but the test says the patient has the disease
Question 4: Describe what Type II error (missed opportunity) represents in this situation.
a. The patient does not have the disease, but the test says the patient has the disease.
b. The patient has the disease, but the test says the patient is healthy.
Answer: B. The patient has the disease, but the test says the patient is healthy.
Question 5: What type of error would you consider to be more serious (i.e. could lead to a more
disastrous outcome)?
a. Type I error
b. Type II error
Answer: B. Type II error
Question 6: When we say that 0.50 is a plausible value for a population proportion (parameter),
plausible means 0.50 will _________.
a. not be in the 95% confidence interval
b. be in the 95% confidence interval
Answer: B. be in the 95% confidence interval
Page 1
, Question 7: Suppose a 95% confidence interval is constructed from a sample proportion and 0.50 is
contained in the interval. Which of the following are true?
a. A 99% confidence interval constructed from the same sample proportion will definitely NOT contain 0.50.
b. A 99% confidence interval constructed from the same sample proportion will definitely contain 0.50.
c. A 90% confidence interval constructed from the same sample proportion will definitely NOT contain 0.50.
d. A 90% confidence interval constructed from the same sample proportion will definitely contain 0.50.
Answer: B. A 99% confidence interval constructed from the same sample proportion will definitely contain
0.50.
Question 8: What proportion of San Luis Obispo (SLO) residents dine at restaurants at least once a
week? To investigate, a local high school student, Deidre, decides to conduct a survey. She selects a
random sample of adult residents of SLO, asks each participant whether he/she dines at restaurants at
least once a week, and records their responses. Then, she uses her data to find a 95% confidence
interval for the proportion of SLO adults who dine out at least once a week to be (0.38, 0.44). The 99%
confidence interval based on the same data would be:
a. Wider, because to be more confident we need to widen the interval.
b. We need more information to answer this.
c. Narrower, because the more confident we are the narrower the interval.
Answer: A. Wider, because to be more confident we need to widen the interval.
Question 9: According to the 95% confidence interval:
a. There is not convincing evidence that less than half of SLO residents dine at restaurants at least once a week,
because the interval does not contain 0.50.
b. There is convincing evidence that less than half of SLO residents dine at restaurants at least once a week,
because the interval does not contain 0.50.
c. Neither of the other choices is correct.
Answer: B. There is convincing evidence that less than half of SLO residents dine at restaurants at least
once a week, because the interval does not contain 0.50.
Question 10: Based on an August 2013 Gallup poll, a 95% confidence interval for the proportion of
American adults that thought math was the most valuable subject they studied in school is 0.31 to 0.37.
Explain exactly what the confidence interval is estimating.
a. The confidence interval is estimating the proportion of all respondents to the poll that thought math was the
most valuable subject they studied in school.
b. The confidence interval is estimating the mean of all American adults that thought math was the most
valuable subject they studied in school.
c. The confidence interval is estimating the mean of all respondents to the poll that thought math was the most
valuable subject they studied in school.
d. The confidence interval is estimating the proportion of all American adults that thought math was the most
valuable subject they studied in school.
Answer: D. The confidence interval is estimating the proportion of all American adults that thought math
was the most valuable subject they studied in school.
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