Free Printable Confidence Intervals for Proportions

Worksheets

Confidence Intervals for Proportions

Total questions: 17

Worksheet time: 41mins

Name

Class

Date

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?

0.53

0.5

0.47

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

(-30.01, 122.01)

(45.87, 46.13)

(.45, .70)

(.29, .55)

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

[.300,.340]

[.298,.342]

[.302,.338]

[.288,.352]

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.

(0.144, 0.296)

(0.190, 0.250)

(0.704, 0.856)

(0.129, 0.311)

A preliminary study suggests that 87% of people agree on an issue. How large must your sample size be so you could be within ± 3% of p calculate at 90% confidence?

466

338

Find the critical value, z* for 97%

1.88

2.17

-1.88

-2.17

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

97%, z* is larger for higher confidence intervals

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

91%, z* is larger for lower confidence intervals

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

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

What is the margin of error of this sample?

0.28

0.14

0.342

0.684

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

What is the point estimate, p̂, of this sample?

0.28

0.14

0.342

0.684

10.

The symbol for the sample proportion is __________.

Z^*

p̂

11.

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?

It gets larger

It gets smaller

It stays the same

Too little information given

12.

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

increasing the confidence level, increasing the sample size

decreasing the confidence level, decreasing the sample size

increasing the confidence level, decreasing the sample size

decreasing the confidence level, increasing the sample size.

13.

The amount added and subtracted to the statistic.

Margin of Error

Point Estimator

Statistic

Population

14.

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

chance variation in choosing a random sample.

undercoverage.

some of the subjects did not understand the questions.

voluntary response.

15.

The 99% confidence interval for a proportion is (0.54, 0.72). What is p̂?

0.63

0.18

0.09

0.66

16.

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

96.52%

0.9652

.9826

98.26%

17.

True or False:

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

True

False

100 %

Confidence Intervals for Proportions

Total questions: 17

Worksheet time: 41mins

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