6) A study is conducted in patients with HIV. The primary outcome is CD4 cell count, which is a measure of the stage of the disease. Lower CD4 counts are associated with more advanced disease. The investigators are interested in the association between vitamin and mineral supplements and CD4 count. A multiple regression analysis is performed relating CD4 count to the use of supplements (coded as 1= yes and 0= no) and to the duration of HIV in years (i.e., the number of years between the diagnosis of HIV and the study date). For the analysis y= CD4 count: Y = 501.41 + 12.67 Supplements - 30.23 Duration of HIV a) What is the expected CD4 count for a patient taking supplements who has had HIV for 2.5 years? I used the example off of page 208 in the textbook for guidance I simply plug 2.5 years in for the duration of HIV. Supplement = 1 and Duration of HIV= 2.5 Y = 501.41 + 12.67 Supplements x 1 - 30.23 x 2.5 years = 438.505 438.5 b) What is the expected CD4 count for a patient not taking supplements who was diagnosed with HIV at study enrollment? I used the example on page 209 for guidance In this problem there are no values to plug in. Supplements=0 and Duration of HIV =0 Y = 501.41 + 12.67 Supplements - 30.23 Duration of HIV= 501.41 c) What is the expected CD4 count for a patient not taking supplements who has had HIV for 2.5 years? There is one value to plug in Supplements =0 and Duration of HIV=2.5 Y = 501.41 + 12.67 Supplements - 30.23 Duration of HIV x 2.5= 438.505 438.5