You conduct a case control study to identify if spicy foods leads to stomach ulcers but you find the people in your study who have stomach ulcers are less likely to eat spicy foods than those without ulcers. you give your participants a food diary and ask them to record the spicy foods they ate last week. mr. smith said sadly as he completed the form, “i just can’teat that stuff anymore.” what guideline for causality may be incorrectly assessed in your study?