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Margin of Error for Proportions

Authored by Anthony Clark

Mathematics

12th Grade

Margin of Error for Proportions
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20 questions

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1.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

Margin of error equals:

Critical Value ∗ standard Error

z*

1.96

Standard Error

2.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

The Gallup Poll interviews 1600 people. Of these,18% say that they jog regularly. The news report adds: “The poll had a margin of error of plus or minus three percentage points at a 95% confidence level.”

You can safely conclude that

95% of all Gallup Poll samples like this one give answers within ±3% of the true population value.

if Gallup took many samples, 95% of them would find that 18% of the people in the sample jog.

the percent of the population who jog is certain to be between 15% and 21%.

95% of the population jog between 15% and 21% of the time.

we can be 95% confident that the sample proportion is captured by the confidence interval.

3.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

A confidence interval for a difference in proportions is −0.077 to 0.013. What are the point estimate and the margin of error for this interval?

–0.032, 0.045

–0.032, 0.090

–0.032, 0.180

–0.045, 0.032

–0.045, 0.090

4.

FILL IN THE BLANK QUESTION

1 min • 1 pt

Many television viewers express doubts about the validity of certain commercials. In an attempt to answer their critics, Timex Group USA wishes to estimate the true proportion p of all consumers who believe what is shown in Timex television commercials. What is the smallest number of consumers that Timex can survey to guarantee a margin of error of 0.05 or less at a 99% confidence level? Round up to the nearest whole number.

5.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

400 randomly selected adults were sampled. The proportion of people who like ice cream was found to be 82%. Find the Margin of Error with 95% confidence for this study. 

0.074

0.192

0.037

0.368

6.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

Complete the equation: 
point estimate +/- _____

standard deviation

margin of error

critical value

confidence level

7.

MULTIPLE CHOICE QUESTION

1 min • 2 pts

A quality control inspector will measure the salt content (in milligrams) in a random sample of bags of potato chips from an hour of production. Which of the following would result in the smallest margin of error in estimating the percent of chips that are too salty?

90% confidence; n = 25 

95% confidence; n =25 

95% confidence; n =50 

90% confidence; n = 50 

n=100 at any confidence level 

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