Question two In the developed world most people with HIV receive some form of "highly active antiretroviral therapy" or

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Question Two In The Developed World Most People With Hiv Receive Some Form Of Highly Active Antiretroviral Therapy Or 1 (245.89 KiB) Viewed 33 times

Question two In the developed world most people with HIV receive some form of "highly active antiretroviral therapy" or HAART. (HAART regimens are basically cocktails of multiple drugs that are more effective because the virus is less likely to become resistant in their presence.) However in underdeveloped nations HAART is rarer because of its cost. Professor Helpful believes that HAART regimens will help reduce the risk of HIV positive pregnant women passing on the infection to their babies and must therefore be aggressively promoted in poor countries. He has followed n=300 HIV positive pregnant women, 100 of whom are receiving at most a basic non-HAART treatment, 100 of whom are taking HAART regimen A, and 100 of whom are taking HAART regimen B. (I'll skip the drug names to keep this simple! He records Y, whether or not the baby is HIV positive (1 = yes, 0 = no) and which treatment regimen the mother was on (X1 = 1 if the mother was on HAART A and 0 otherwise, X2 = 1 if mother was on HAART B and 0 otherwise), and fits a logistic regression. The corresponding STATA printouts are below. Use them to answer the following questions. 23 • logit HIVplus HAART_A HAART_B Logistic regression Number of obs LR chi2(2) Prob > chi2 Pseudo R2 300 6.75 0.0342 0.0339 Log likelihood - -96.32681 HIVplus Coef. Std. Err. z P>12! [95% Conf. Interval] HAART_A1 HAART_B -0.539 -1.286 .431 .534 -1.25 -2.41 0.211 0.016 -1.383 -2.332 0.305 -0.240 cons -1.658 .273 -6.08 0.000 -2.193 -1.124 • logistic HIVplus HAART_A HAART_B Logistic regression Number of obs LR chi2(2) Prob > chi2 Pseudo R2 300 6.75 0.0342 0.0339 Log likelihood - -96.32681 hivplus Odds Ratio Std. Err. Z P>z! (95% Conf. Interval] HAART_A1 HAART BI .583 .276 .251 147 -1.25 -2.41 0.211 0.016 .251 .097 1.357 0.787 (a) Overall, is treatment regimen useful for explaining whether a woman passes on HIV infection to her baby? Write down the mathematical hypotheses you are testing, circle the relevant p-value on one of the printouts and give your real-world conclusions using a =.05. You do NOT need to provide any other details. (b) Give a brief interpretation of the odds ratio for the HAART A variable and show how to compute it from the first regression printout. (c) Do HAART A and HAART B appear to reduce a mother's risk of passing on HIV to her infant? Explain briefly using a = .05 and give the p-values corresponding to the tests you are performing. You do NOT need to write out any other details of the tests. (d) Find the odds ratio comparing the risk of HIV transmission for mothers in the HAART A group compared to those in the HAART B group. Show your work. Based on this estimate which of these treatment regimens is more effective? Briefly explain your reasoning. Do you think you can be 95% sure this treatment is better? Explain. ~~~ THE END ~~~ "Success is no accident. It is hard work, perseverance, learning, sacrifice and most of all, love of what you are doing or learning to do." - Edson Arantes do Nascimento. 33