Posted by **Nick** on Sunday, October 27, 2013 at 6:48pm.

Direct mail advertisers send solicitations (that is "junk mail") to thousands of potential customers in the hope that some will buy the company's products. The response rate is usually quite low. Suppose a company wants to test the response rate for a new flyer format. The company randomly selects 1000 from its mailing list of over 200,000 people. Their sample results in orders from 112 people.

Create a 90% confidence interval for the percentage of people the company contacts who may buy something.

The 90% confidence interval is % to %.

What is the margin of error? The margin of error is %. Show your answers as percents rounded to TENTHS of a percent. Do not type in the % sign.

How do I find the confidence interval? Once I get this do I just subtract the intervals to get the margin of error?

- Statistics -
**Kuai**, Sunday, October 27, 2013 at 7:11pm
n = 1000

x = 112

p = x/n

p = 112/1000 = 0.112

z critical value = 1.645

E = za/2 *sqrt((p (1-p)/)/n))

E = 1.645 *sqrt((.112*.888/1000)

E = 0.016

p ± ('z critical value') * SQRT[p * (1 - p)/n] = 0.112 ± 1.645 * SQRT[0.112 * (1 - 0.112)/1000] = [0.096, 0.128]

The 90% confidence interval is 12.8% to 9.6%

- Statistics -
**Nick**, Sunday, October 27, 2013 at 7:20pm
Wow! Thank you for the help! Also, wouldn't the 90% confidence interval be 9.6% to 12.8%? Also, would the margin of error be 3.2 or 1.6?

Thank you!

- Statistics -
**Kuai**, Sunday, October 27, 2013 at 10:50pm
The 90% confidence interval is 9.6 % to 12.8%.

The margin of error is 1.6.

## Answer This Question

## Related Questions

- Statistics - Direct mail advertisers send solicitations (a.k.a. "junk mail") to ...
- statistics - A telephone company representative estimates that 40% of its ...
- science - Find and save a piece of junk mail. What is this piece of mail trying ...
- statistics - On average, you receive four pieces of junk mail a day. For a ...
- statistics - Five percent of all items sold by a mail-order company are returned...
- statistics - Five percent of all items sold by a mail-order company are returned...
- statistics - Five percent of all items sold by a mail-order company are returned...
- statistics - Three percent of all items sold by a mail-order company are ...
- statistics - Five percent of all items sold by a mail-order company are returned...
- statistics - Five percent of all items sold by mail order company are returned ...

More Related Questions