Determine whether this situation represents negative confounding or positive confounding. A group of researchers is investigating the relationship between vitamin D supplementation and the risk of osteoporosis among postmenopausal women. They conduct a randomized controlled trial (RCT) where 500 women are randomly assigned to either receive vitamin D supplements or a placebo for a duration of one year. After the trial period, bone mineral density (BMD) measurements are taken for all participants. Surprisingly, the results show that the group receiving the vitamin D supplements has a higher incidence of osteoporosis compared to the placebo group (RR = 1.34). Further analysis reveals that a significant proportion of women in the supplement group also have a sedentary lifestyle and low calcium intake, both known risk factors for osteoporosis (RR = 1.03)