A study was conducted in 100 children to assess risk factors for obesity. Sixty-

Question

A study was conducted in 100 children to assess risk factors for obesity. Sixty-two (62) children were normal weight (body mass index < 25), and 38 children were overweight/ obese (body mass index > 25). The investigators were interested in determining whether there was a statistically significant difference in the mean age of the normal weight versus overweight/ obese children. What is the name of the most appropriate statistical test to determine whether there is a significant difference in mean age between the normal weight versus overweight/ obese children? Why did you select this test? Also is a one-sided or two-sided test more appropriate and why?

Explanation / Answer

The most appropriate statistical test to determine the difference in mean age between the normal weight versus overweight/ obese children is a two sample z test which is used to determine if two sample means are equal or unequal.

As, n is large enough (so approximately normally distributed) andt his is called a two-sample situation and is one of the most common settings in statistical applications. Responses in each group is independent of those in the other, meaning that different, unrelated, unpaired individuals make up the two samples so we will use the z test.

This is a two sided test i.e.

Null hypothesis: H 0: 1 - 2 = 0

alternative hypothesis: H a: 1- 2 0

If the null hypothesis is rejected we can conculde that here was a statistically significant difference in the mean age of the normal weight versus overweight/ obese children at some significance level and vice versa.

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