A nutritionist is interested in studying the effect of diet on weight loss in women with PCOS. In order to establish a causal relationship between diet and weight loss, the nutritionist would need to conduct a: Double-blind observational study. Non-randomized experimental design in which the examining nutritionist is blinded to the diet subjects with PCOS are on. Comparative randomized experiment. O Survey questionnaire to be administered to all of the nutritionist's clients who have PCOS