We have the survey data on the body mass index (BMI) of 646 young women. The mea

Question

We have the survey data on the body mass index (BMI) of 646 young women. The mean BMI in the sample was  x¯= 26.8 . We treated these data as an SRS from a Normally distributed population with standard deviation = 7.2.    

Give confidence intervals for the mean BMI and the margins of error for 90%, 95%, and 99% confidence.

Conf. Level Interval ( ± ± 0.01) margins of error ( ± ± 0.0001) 90% to 95% to 99% to

           _________

Conf. Level Interval (±± 0.01) margins of error (±± 0.0001) 90% _____to ______            ________ 95% _____to______          __________ 99% _____to______

           _________

Explanation / Answer

Answers to all the parts being asked:

n=646
xbar = 26.8
Sigma = 7.2

Confidence level of 90%, 95%, and 99%

1. The interval is and Margin of error is @ 90%?
26.8 +/- 1.28*(7.2/sqrt(646))
=26.4374 to 27.1626

Margin of error = .3626

2. The interval is and Margin of error is @ 95%?
26.8 +/- 1.96*(7.2/sqrt(646))
=26.245 to 27.355

Margin of error =1.96*(7.2/SQRT(646))
=.5552

3. The interval is and Margin of error is @ 99%?
26.8 +/- 1.28*(7.2/sqrt(646))
=26.069 to 27.531

Margin of error =2.58*(7.2/SQRT(646))
=.7309

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