Quiz about Confidence Intervals for Proportions

Question 1

A random sample of 100 WHS students found that 53 of them were in possession of a pencil. What is the p-hat for this sample?

Accepted Answer

0.53

Answer

0.5

Answer

0.47

Answer

1

Question 2

A survey of 80 recent fatal traffic accidents showed that 46 were alcohol-related. Find the 98% CI.

Accepted Answer

(.45, .70)

Answer

(-30.01, 122.01)

Answer

(45.87, 46.13)

Answer

(.29, .55)

Question 3

If 827 represents "no" voters out of 2584, construct a 95% confidence interval for the "no" group.

Accepted Answer

[.302,.338]

Answer

[.300,.340]

Answer

[.298,.342]

Answer

[.288,.352]

Question 4

A nutritionist found that in a sample of 80 families, 22% said they are apples at least once a week. Construct the 90% CI for the population proportion.

Accepted Answer

(0.144, 0.296)

Answer

(0.190, 0.250)

Answer

(0.704, 0.856)

Answer

(0.129, 0.311)

Question 5

Find the critical value, z* for 97%

Accepted Answer

2.17

Answer

1.88

Answer

-1.88

Answer

-2.17

Question 6

Which confidence would result in a wider interval (assuming nothing else changed), 91% or 97%?

Accepted Answer

97%, z* is larger for higher confidence intervals

Answer

97%, the standard error is larger for higher confidence intervals

Answer

91%, z* is larger for lower confidence intervals

Answer

91%, the standard error is smaller for lower confidence intervals

Question 7

For a sample, the 95% confidence interval is (0.202, 0.482).

What is the margin of error of this sample?

Accepted Answer

0.14

Answer

0.28

Answer

0.342

Answer

0.684

Question 8

A research company wants to estimate the proportion of people who like oatmeal.  They want the confidence level to be 95%.  The company gets 325 people to sign up for the survey, but on the day that the survey is issued, only 250 people show up and take the survey.  What happens to the confidence interval?

Accepted Answer

It gets larger

Answer

It gets smaller

Answer

It stays the same

Answer

Too little information given

Question 9

Which of the following changes to a study would result in a narrower confidence interval?

Accepted Answer

decreasing the confidence level, increasing the sample size.

Answer

increasing the confidence level, increasing the sample size

Answer

decreasing the confidence level, decreasing the sample size

Answer

increasing the confidence level, decreasing the sample size

Question 10

The amount added and subtracted to the statistic.

Accepted Answer

Margin of Error

Answer

Point Estimator

Answer

Statistic

Answer

Population

Question 11

Which of the following sources of error is included in the margin of error

Accepted Answer

chance variation in choosing a random sample.

Answer

undercoverage.

Answer

some of the subjects did not understand the questions.

Answer

voluntary response.

Question 12

Given the Critical Value of z^* = 2.11, find the Confidence Level.

Accepted Answer

96.52%

Answer

0.9652

Answer

.9826

Answer

98.26%

Question 13

True or False:

The more confident you want to be, the smaller your confidence interval will be.

Accepted Answer

False

Answer

True

Confidence Intervals for Proportions

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