**Week 6**

Assignment: Estimating Sample Size for a Population Proportion

Assignment: Estimating Sample Size for a Population Proportion

**Calculate the sample
size required to estimate a population proportion with a given confidence level**

**Question**

Suppose a clothing store wants to determine

the current percentage of customers who are over the age of forty. How many

customers should the company survey in order to be92% confident that the estimated (sample)

proportion is within5 percentage

points of the true population proportion of customers who are over the age of forty?

z0.16 |
z0.08 |
z0.04 |
z0.02 |
z0.01 |

0.994 |
1.405 |
1.751 |
2.054 |
2.326 |

Use the table of values above.

**
**

Yes that’s right. Keep it up!

307

91

198

77

614

**Calculate the sample size required to estimate a population
proportion with a given confidence level**

## Question

Suppose an automotive repair company wants to determine the

current percentage of customers who keep up with regular vehicle maintenance.

How many customers should the company survey in order to be 90% confident

that the estimated (sample) proportion is within 2 percentage

points of the true population proportion of customers who keep up with regular

vehicle maintenance?

z0.10 |
z0.05 |
z0.025 |
z0.01 |
z0.005 |

1.282 |
1.645 |
1.960 |
2.326 |
2.576 |

Use the table of values above.

**423**

**609**

**1,028**

**1,692**

**3,383**

**Calculate the sample size required to estimate a population
proportion with a given confidence level**

**
**

## Question

Suppose

an automotive repair company wants to determine the current percentage of

customers who keep up with regular vehicle maintenance. How many customers

should the company survey in order to be 95% confident that

the estimated (sample) proportion is within 2 percentage

points of the true population proportion of customers who keep up with regular

vehicle maintenance?

z0.10 |
z0.05 |
z0.025 |
z0.01 |
z0.005 |

1.282 |
1.645 |
1.960 |
2.326 |
2.576 |

Use the table of values above.

322

601

1,692

2,401

9,604

**Calculate the sample size required to estimate a population
proportion with a given confidence level**

## Question

Virginia

wants to estimate the percentage of students who live more than three miles

from the school. She wants to create a 95% confidence

interval which has an error bound of at most 5%. How many students

should be polled to create the confidence interval?

z0.10 |
z0.05 |
z0.025 |
z0.01 |
z0.005 |

1.282 |
1.645 |
1.960 |
2.326 |
2.576 |

Use the table of values above.

52

73

97

271

385