13 Turn over 6 A formula meal is a calorie controlled drink. The results of a clinical trial were published in September 2018. The trial compared weight loss of adult patients assigned randomly either to Diet A, based only on formula meals, or to Diet B, based only on conventional meals. (a) Define a double blind trial. Explain why it was not possible for this clinical trial to be double blind. (2) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ The mean weight loss after one year for each group is shown in Figure 5, together with the sample standard deviation of weight loss for each group. Sample sizes for each diet are also given. Diet A Diet B Mean weight loss, x, kg 10.7 3.1 Sample standard deviation of weight loss, s, kg 9.6 7.0 Sample size, n 104 95 (Source: British Medical Journal) Figure 5 (b) Conduct a hypothesis test to determine whether the mean weight loss of patients assigned to Diet A is different from that of patients assigned to Diet B. (7) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________