# Confidence Interval Estimation

*label*Mathematics

*timer*Asked: Jun 28th, 2018

*account_balance_wallet*$20

**Question description**

Confidence Interval Estimation – Discussion

When the results of a survey or poll are published, the sample size and the margin of error are both given. For example: 1000 voters were surveyed and 39±2% of the voters agree with the president. In this example N=1000 and the margin of error (MoE) is 2%.

This website lists several public opinion polls. Search the site and find a poll where the sample size and margin of error are given. Try to find a poll dealing with a topic in your profession or one in which you are really interested.

Determine the following information for the selected poll results and include in your initial post:

- URL for the website. State the poll question, the sample size N, and the margin of error (also known as sampling error).
- Interpret the results of your poll using your own words and full sentences. Note: Depending on the question asked, your poll may have more than one poll result – you only need to discuss one result.
- State the confidence interval using the MoE. What does this confidence interval estimate?
- Use this worksheet (click to download CIE Proportion.xlsx) to calculate the confidence interval based on the sample size and the number of successes (the proportion you are interested in). Use a confidence level of 95%.
- What is the calculated confidence interval? How does this compare to the interval in part 3 using the poll’s MoE?
- Discuss potential biases that could skew sampling results.

First response: Choose a classmate’s post. Calculate the sample size needed for the given MoE and see if the poll had enough people surveyed. Use this worksheet (click to download Sample Size Proportion.xlsx) to find the sample size needed.

Second response: Choose another classmate’s post. Change the confidence level to 90% or 99%. What happened to the confidence interval (compared to your classmate’s)? Explain the change.

## Tutor Answer

See attached. I have already posted to the campus site.

Hello everyone.

For my Topic, I chose climate change since I am a firm believer in the protection of the

environment.

1. URL for the website. State the poll question, the sample size N, and the margin of error (also

known as sampling error).

URL: http://www.pollingreport.com/enviro.htm

Poll question: "Do you support or oppose Donald Trump's decision to withdraw

from the main international agreement that tries to address climate change?"

The poll was conducted by ABC News/Washington Post Poll on June 2-4, 2017.

N=527 adults nationwide. Margin of error = ± 5.

2. Interpret the results of your poll using your own words and full sentences. Note: Depending

on the question asked, your poll may have more than one poll result – you only need to

discuss one result.

The results of the ...

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