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January 27, 2015

January 27, 2015

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

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 7:11pmn = 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 7:20pmWow! 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 10:50pmThe 90% confidence interval is 9.6 % to 12.8%.

The margin of error is 1.6.

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