1. i) AIC, ORIC and New method use information criteria and select the models with the largest adjusted log-likelihood. ii) MCT defines different contrasts for all elementary alternative models and test all of them in a multiple contrast test; after rejecting the null for at least one alternatives, select the one with largest test statistics. Model Selection under Change Point Order Restriction Xuefei Mi, L.A. Hothorn Institute of Biostatistics, Leibniz University Hannover, Germany 1. Change-point detection Example Objectives to control the familywise error rate over all k-1 alternative models ii) When the null is rejected at level α, select one of the elementary model 3. Competing approaches i) Common AIC (Akaike, 1973) ii) Order restricted information criteria (Anraku, 1999) iii) Multiple Contrast Test (MCT) （ Bretz and Hothorn, 2002 ） The test statistics under different alternatives is: iv) Non-parametric idea (Xiong and Barmi, 2002) Similar idea, but calculate the penalty by simulation 6. Conclusions i) Model selection approaches for some ordered alternatives modified in such a way that it controls α. ii) Global decision AND decision in favor of a particular elementary alternative model Email: mi@biostat.uni-hannover.de References: Anraku, K. An information criterion for parameters under a simple order restriction. Biometrika, 1999;86: 141-152 Akaike,H. Information theory and an extension of maximum likelihood principle. Second International Symposium on Information. Theory Akademia Kiado, 1973:267-281 Bretz, F and Hothorn, L.A. Detecting dose response using contrasts: asymptotic power and sample size determination for binomial data. Statist. Med., 2002;21:3325 Ninomiya, Y Information criterion for Gaussian change-point model Stat. Probability Lett., 2005;72: 237-247 Ninomiya, Y Personal communication 2006 2. Decompose the global alternative into all elementary ones The maximum likelihood estimator under order restriction for different elementary alternatives, calculated by pool-adjacent-violators algorithm (Robertson, 1988) The estimated information are used to identify the “true” model, calculated from the log-likelihood of estimators. Kullback-Leibler Distance (Anraku, 1999) The constant term is omitted. The model, which has the largest (-KL) distance, is selected as the most possible model. The distribution of the log-likelihood (Robertson, 1988) Our new penalty term 5. Epedemic alternatives: Two change-points In DNA motif finding is assumed to be binomial distributed Epidemic alternative Approximately penalty term for the alternatives (Ninomiya, 2005) penalty= 2+3m m is the number of change-points E.g. for symmetric motif 4. Local decision: Model selection controlling α Evaluation of the example: Anraku method is a sensitive one to detect the change-point, but the over estimate problem is discussed by Roberts(2006). Hypothesis 0.49 0.45 0.51 0.445 0.58 New vs. MCT - Higher power than MCT - Simpler and faster - MCT provides confidence intervals New vs. Anraku - Controls the α rate - Does not over-estimate Robertson, T., Wright, F.T. and Dykstra, R.L. Order restricted statistical inference. Wiley, New York. 1988. Roberts, S. and Martin, M.A. The question of nonlinearity in the dose-response relation between particulate matter air pollution and mortality: can Akaike’s Information Criterion be trusted to take the right turn? American Journal of Epidemiology 2006;164:No. 12 Stormo G, Schneider T, Gold L, Ehrenfeucht A. Use of the ’perception algorithm to distinguish translational initiation sites in Escherichia coli Nucleic Acids Res, 1982;10:2997-3011 VanZwet E. Kechris, KJ. Bickel, PJ. et al. Estimating motifs under order restrictions. Statistical Applications in Genetics and Molecular Biology, 2005;4:1 Xiong, C. And Barmi, H. On detecting change in likelihood ratio ordering. Nonparametric Statistics 2002;14: 555-568 Zhu J. and Zhang M. A Promoter database of yeast Saccharomyces cerevisiae. Bioinformatics 1999; 15:607-611. Dose finding study with an adverse events rate by Bretz and Hothorn (2002) Special case of order restriction: one change- point