Is this a randomized comparitive experiment or matched pairs experiment?And If the study had included 500 participants instead of 75, would you expect the confidence interval to be wider or narrower?

View Policies Current Attempt in Progress Bisphenol A in Your Soup Cans Bisphenol A (BPA) is in the lining of most canned goods, and recent studies have shown a positive association between BPA exposu and behavior and health problems. How much does canned soup consumption increase urinary BPA concentration? That was the question addressed in a recent study in which consumption of canned soup over five days was associated with a more than 1000 increase in urinary BPA. In the study, 75 participants ate either canned soup or fresh soup for lunch for five days. On the fifth day, urinary BPA levels were measured. After a two-day break, the participants switched groups and repeated the process. The differen in BPA levels between the two treatments was measured for each participant. The study reports that a 95 % confidence interval fo the difference in means (canned minus fresh) is 19.6 to 25.5 pg/L. 1Carwile J., Ye X., Zhou X., Calafat A., and Michels K., "Canned Soup Consumption and Urinary Bisphenol A: A Randomized Crossove Trial," Journal of the American Medical Association, 2011; 306(20): 2218-2220. (a) Is this a randomized comparative experiment or a matched pairs experiment