Comparison between two diets in obese children, one low-fat and one low-carb 8 week intervention with the outcome of weight loss. Based on a similar study in adults, 20% of the children will not complete the study. For a 95% confidence interval with a margin of error of no more than 3 lbs., how many children should be recruited? In the adult trial, the low-fat and low-carb groups had a standard deviations of 8.4 and 7.7, respectively and each group had 100 participants.

A. Calculate the pooled standard deviation (Sp).

B. Calculate the number of children will need to be recruited for the trial if all finish the study use the Sp calculated for the standard deviation?

C. How many children would be needed to account for 20% attrition.