Activity 5: More practice making confidence intervals The mean BMI (Body Mass In

Question

Activity 5: More practice making confidence intervals The mean BMI (Body Mass Index) for a large sample of US adults is 27.655. we are told that the standard error for this estimate is 0.009. If we use the normal distribution to find a 99% confidence interval for the mean BMI of US adults 1. (a) What is? (b) Find and interpret the 99% confidence interval. Using the same sample, the difference in mean EMI between non-exercisers (those who said they had not exerosed at all in the last 30 days) and exerdisers (who said they had exercised at least once 2. in the last 30 days) is -x-1.015 , with a standard error for the estimate of SE = 0.016. If we use the normal distribution to find a 90% confidence interval for the difference in mean BMI between the two group:s: (a) What isz*? (b) Find and interpret the 90% confidence interval.

Explanation / Answer

Mean is 27.655 and s is 0.009

a) z is given as 2.575 for 99% confidence

b) lower limit is mean-s*z=27.655-2.575*0.009=27.631825

and upper limit is mean+s*z=27.655+2.575*0.009 =27.678175

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