veral studies have been performed relating urinary potassium excretion to blood - ressure level. These studies have tended to show an inverse relationship between Lese two variables, with the higher the level of potassium excretion, the lower the P level. Therefore , a treatment trial is planned to look at the effect of potassium take in the form of supplement capsules on changes in DBP level. Suppose that in a .lot study, 20 pe0ple are given potassium supplements for 1 month. The data are as llows: Mean change (1 monthbaseline) sd change Il a) Test to assess if potassium supplements have any effect on DBP level? b) Derive a 95% CI for the true mean change based on the preceding data. What is the relationship of your results here and in a? :c) How many subjects need to be studied to have an 80% chance of detecting a significant treatment effect using a two-sided test with an 0: level of .05 if the mean and sd of the pilot study are assumed to be the population mean and sd? a study of the natural history of retinitis pigmentosa (RP), 94 RP patients were llowed for 3 years. Among 90 patients with complete followup, the meani 1 se of (visualfield loss) over 1, 2, and 3 years was 0023: 0.04 , 008 i: 0.05 , and 014 d: 07 , respectively. a) Test for changes in visual field over 1 year. b) Test for changes in visual field over 2 years. :c) Test for changes in visual field over 3 years. :fer to the data below : Left heart disease Normals Mean sd 11 Mean sd n THW (g) 450.00 139.34 11 317.00 47.09 10 BW (kg) 55.61 11.55 11 56.23 11.54 10 a) Assuming unequal variance, test for a significant difference in mean total heart weight (THW) between the disease and normal groups. b) Assuming equal variance, test for a significant different in mean body weight (BW) between the diseased and normal groups