25 groups with 7 people in each group, join "The Greatest Loser" competition. Based on the greatest percent of weight loss, the greatest loser wins. Calculations regarding percentages are made by taking the total weight of the group and dividing by 7. Weignts are measured initially and after 9 weeks.
A new group comes along and that only has 5 people. Their weights are also measured initially and after 9 weeks. What would be the most accurate methodology for determining the percentage of weight loss for this new group?