From ssubra at yahoo.com Wed Jun 16 11:53:06 2010 From: ssubra at yahoo.com (Subramanian Swaminathan) Date: Wed, 16 Jun 2010 02:53:06 -0700 (PDT) Subject: [Mailman] simulating binary random numbers Message-ID: <525082.50244.qm@web38506.mail.mud.yahoo.com> Dear R-friends, I just started learning R. I have a project on lot quality assurance sampling (LQAS). In this project I?have to develop LQAS?plans to make decision on stopping / continuing a programme. The LQAS plans is based on?cluster sampling:?selection of k clusters (villages) of m children?each?for a total sample of n. In this connection?I would like to estimate the classification errors ( alpha and beta) that would be expected as a consequence of sampling clusters (villages / households) instead of usual SRS?under traditional LQAS.?In order to estimate the?classification errors I would like to simulate correlated binary outcomes for a given level of prevalence?and intracluster correlation (rho). Specifically I would like simulate?an LQAS plan?(33 clusters of 6 children each,?n =198 children) to generate?clusters with specific intercluster (0.05) and intracluster correlation (0.1) subject to the constraint that the?intercluster correlation?is less than or equal to intracluster correlation for a given?level of prevalence?(upper threshold =1% and lower threshold=0.1%). For this purpose I have used?the following command (which is under mvtBinaryEP?in mvtnorm library in R): ep0 = ep(mu=0.1, rho=0.05, n=6, nRep=33, seed=NULL) apply(ep0$y, c(1,2), mean); cor(ep0$y) The above commands produce?198 binary outcomes?(33 clusters with cluster size of 6 each) and a matrix (6x6) of bivariate correlations.?Since the input?among others requires values either?for 'rho' along with 'mu' or an 'R' matrix and a?column vector of 'mu', I wonder whether the binary outcomes?meets my?specification?about inter-cluster correlation. I would?be very much grateful to R-community, if someone helps me out. thanking you in advance and I?am looking forward?to R-community subramanian ========== Dr S.Subramanian Assistant Director Vector Control Research Centre Indira Nagar Pondicherry - 605 006 INDIA? -------------- next part -------------- An HTML attachment was scrubbed... URL: