Introductory Biostatistics Homework 15 1. HbsAg is a surface angigen of the Hepatitis-B-Virus (HBV) which indicates current Hepatitis B infection. Seropositivity of HbsAg in 334 patients with lymphoproliferative disorders and a controlgroup of 802 patients were obtained. Results appear in the table below. c. d. e. Group Total Patients Controls HbsAg positive 1075 1 13 6 HbsAg negative Total . Consider a chi-square test run on this table. What would be the null and alternative hypotheses of the test? . Can we make causal inference about the effect of lymphoprolifer-ative disorders on HbsAg status (positive vs. negative) basedonthese data? Why or why not. Calculate the expected values for each cell in the table,that is E 11 ,E 12.13 21 , E 22. Calculate the Pearson Chi-square statistic for these data. What are your conclusions? 2. A random sample of n=200 patients admitted to an adult intensive care unit were evaluated on a range of variables to determine predictors of Intensive Care Unit (ICU) mortality. Below is a table of survival status by gender. a. b. Gender Male Female What are the odds of survival for men admitted to the unit? What are the odds of survival for women admitted to the unit? What is the odds ratio of survival for men compared to women? Which group is doing worse? . Using Stata, conduct a chi-square test to evaluate differences between the genders at the 0.05 signicance level. Give your test statistic, degrees of freedom, and conclusions of the test