Select all of the responses which are correct

Which of the following is/are true regarding logistic regression?

a. This technique is most often used to analyze data from large, prospective cohort studies.

b. Interpretation of the results for a variable included in a multivariate logistic regression model should always include the direction of the association, whether or not it is statically significant, and a statement that this is the observed relationship after controlling for the other factors in the model.

c. If the R2 value for a multivariate logistic regression model is 0.24, p = 0.001, we can accept the alternate hypothesis that that the set of independent variables included in the model explains more than 0% of the variance in the dependent variable.

d. Logistic regression would be ideal for analysis of a clinical trial of a new drug compared with a placebo that enrolls subjects over a two-year period and continues until 4444 outcome events have been accumulated.

General Techniques and Notation 1. Pay attention to stationary distribution of a birth-and-death process associated with queuing system. 2. If necessary, validate the identity L = A . W, where L = E [X ()] under stationary distribution, and W is the average waiting time for a service request. 3. Main objectives are related to systems with a single server, M/M/1 and with unlimited number of servers, M/M/co. 4. Hints are presented in the document titled Notes: Part 8. If you encounter difficulties, please contact me via email before the submission deadline!Problem 2 In a queueing system there is one sewer. Customers arrive at the queueing system according to a Poisson process with arrival rate 20 customers per hour. An arriving customer nding to people in the system, immediately leaves with probability Tl: ,,_=, n=,l,...,4. q 4 Customers that join the system are served in order of arrival and the service times are assumed to be independent and exponentially distributed with a mean service time equal to 3 minutes. Let X (t) denote the number of customers in the system at time t. Assume that X(U] = D. a] Explain why X (t) is a birth and death process and give the birth and What is the probability that the rst customer has departed the queue- ing system before the next customer arrives? b] 1What is the expected time until the rst customer arrives at the queue ing system? What is the expected time until there is, for the rst time, 4 customers in the system? c] Explain why the limiting distribution of X (t) exists and show that this distribution is given by 32 32 24 12 3 P= P= P= P= P=. \" 103' 1 103' 2 103' 3 103' 4 103 d] In the long run: i) What is the probability that an arriving customer will join the queueing system and not leave immediately? ii) 'What is the mean number of customers in the queueing system? iii) What is the mean time customers that are served, spend in the system