http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/495 2013-05-22T22:51:51Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/2858 Threshold Autoregressive Model for a Time Series Data Kesavan Nampoothiri, C; Balakrishna, N In this paper we try to fit a threshold autoregressive (TAR) model to time series data of monthly coconut oil prices at Cochin market. The procedure proposed by Tsay [7] for fitting the TAR model is briefly presented. The fitted model is compared with a simple autoregressive (AR) model. The results are in favour of TAR process. Thus the monthly coconut oil prices exhibit a type of non-linearity which can be accounted for by a threshold model. 2000-01-01T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/2857 Nonparametric Estimation of the Average Availability Balakrishna, N; Angel, Mathew The average availability of a repairable system is the expected proportion of time that the system is operating in the interval [0, t]. The present article discusses the nonparametric estimation of the average availability when (i) the data on 'n' complete cycles of system operation are available, (ii) the data are subject to right censorship, and (iii) the process is observed upto a specified time 'T'. In each case, a nonparametric confidence interval for the average availability is also constructed. Simulations are conducted to assess the performance of the estimators. 2009-01-01T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/2856 Computationally Efficient Bootstrap Prediction Intervals for Returns and Volatilities in ARCH and GARCH Processes Chen, Bei; Gel, Yulia R; Balakrishna, N; Abraham, Bovas We propose a novel, simple, efficient and distribution-free re-sampling technique for developing prediction intervals for returns and volatilities following ARCH/GARCH models. In particular, our key idea is to employ a Box–Jenkins linear representation of an ARCH/GARCH equation and then to adapt a sieve bootstrap procedure to the nonlinear GARCH framework. Our simulation studies indicate that the new re-sampling method provides sharp and well calibrated prediction intervals for both returns and volatilities while reducing computational costs by up to 100 times, compared to other available re-sampling techniques for ARCH/GARCH models. The proposed procedure is illustrated by an application to Yen/U.S. dollar daily exchange rate data. 2011-01-01T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/2855 Statistical signal extraction using stable processes Balakrishna, N; Hareesh, G The standard models for statistical signal extraction assume that the signal and noise are generated by linear Gaussian processes. The optimum filter weights for those models are derived using the method of minimum mean square error. In the present work we study the properties of signal extraction models under the assumption that signal/noise are generated by symmetric stable processes. The optimum filter is obtained by the method of minimum dispersion. The performance of the new filter is compared with their Gaussian counterparts by simulation. 2009-01-01T00:00:00Z