Question

In: Statistics and Probability

An article presents results of a survey of adults with diabetes. The average body mass index...

An article presents results of a survey of adults with diabetes. The average body mass index (BMI) in a sample of 15 men was 30.4, with a standard deviation of 0.6. The average BMI in a sample of 19 women was 31.1 with a standard deviation of 0.2. Assuming BMI is normally distributed, find a 95% confidence bound for the difference in mean BMI between men and women with diabetes. Be sure to interpret the interval in context.

Solutions

Expert Solution

We need to construct the 95% confidence interval for the difference between the population means μ1​−μ2​, for the case that the population standard deviations are not known. The following information has been provided about each of the samples:

Based on the information provided, we assume that the population variances are equal, so then the number of degrees of freedom are

The critical value for α=0.05 and df=32 degrees of freedom is

Therefore, based on the data provided, the 95% confidence interval for the difference between the population means μ1​−μ2​ is −0.998<μ1​−μ2​<−0.402, which indicates that we are 95% confident that the true difference between population means is contained by the interval (−0.998,−0.402).

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