Mr. Krabs wants to make Bikini Bottoms a more pleasant place to live. He has created a new sauce that he thinks will reduce body gas production by eating grumpy Krabs burgers. Recruit 100 clients with a history of gas problems. 50 of them (Group A) eat empanadas in a bad mood with the new sauce. The other 50 (Group B) started crabby patties with sauce that looks like a new sauce, but is really just a mixture of mayonnaise and food coloring. Both groups were told that they were receiving the sauce that would reduce gas production. Two hours after eating the crab patties, 30 customers in Group A reported fewer gas problems and 8 customers in Group B reported fewer gas problems. What is the independent variable?