Ann. Inst. Statist. Math. Vol. 57, No. 4, 789-802 (2005) (~)2005 The Institute of Statistical Mathematics INFERENCES BASED ON A BIVARIATE DISTRIBUTION WITH VON MISES MARGINALS GRACE S. SHIEH I AND RICHARD A. JOHNSON2 l Institute of Statistical Science, Academia Sinica, Taipei 115, Taiwan, R. O. C., e-mail: gshieh@stat .sinica.edu.tw 2Department of Statistics, University of Wisconsin-Madison, WI 53706, U.S.A., e-mail:
[email protected] (Received April 21, 2004; revised August 24, 2004) Abstract. There is very little literature concerning modeling the correlation be- tween paired angular observations. We propose a bivariate model with von Mises marginal distributions. An algorithm for generating bivariate angles from this von Mises distribution is given. Maximum likelihood estimation is then addressed. We also develop a likelihood ratio test for independence in paired circular data. Applica- tion of the procedures to paired wind directions is illustrated. Employing simulation, using the proposed model, we compare the power of the likelihood ratio test with six existing tests of independence. Key words and phrases: Angular observations, maximum likelihood estimation, models of dependence, power, testing. 1. Introduction Testing for independence in paired circular (bivariate angular) data has been ex- plored by many statisticians; see Fisher (1995) and Mardia and Jupp (2000) for thorough accounts. Paired circular data are either both angular or both cyclic in nature. For in- stance, wind directions at 6 a.m. and at noon recorded at a weather station for 21 consecutive days (Johnson and Wehrly (1977)), estimated peak times for two successive measurements of diastolic blood pressure (Downs (1974)), among others.