A simulation study of a parametric mixture model of three different distributions to analyze heterogeneous survival data

In this paper a simulation study of a parametric mixture model of three different distributions is considered to model heterogeneous survival data.Some properties of the proposed parametric mixture of Exponential, Gamma and Weibull are investigated.The Expectation Maximization Algorithm (EM) is implemented to estimate the maximum likelihood estimators of three different postulated parametric mixture model parameters.The simulations are performed by simulating data sampled from a population of three component parametric mixture of three different distributions, and the simulations are repeated 10, 30, 50, 100 and 500 times to investigate the consistency and stability of the EM scheme.The EM Algorithm scheme developed is able to estimate the parameters of the mixture which are very close to the parameters of the postulated model.The repetitions of the simulation give parameters closer and closer to the postulated models, as the number of repetitions increases, with relatively small standard errors

Models of air passenger traffic flows: A comparison of their forecasting effectiveness

Airline traffic forecasting in the medium term is important to airlines and regulatory authorities that attempt to plan and schedule capacity.This research examines a number of alternative approaches to forecasting short to medium term (1 to 3 years) air traffic flows.The data examined are flows between the UK and six other countries over the period of 1961-2002, which has seen substantial changes in both transport technology and economic development.The economic drivers, under consideration, are price, GDP and bilateral trade.The forecasting models employed include autoregressive models, autoregressive distributed lag models specified using various statistical and economic criteria and a newly developed automatic method for model specification (PcGets), as well as time varying parameter models. Various approaches to including interactions between the contemporaneous air traffic flows are examined including pooled autoregressive distributed lag models and the inclusion of a ‘world’ variable that measures overall trade growth in the world economy.Based on the analysis of forecasting error measures, it is concluded that time varying parameter models that include the ‘world’ variable with an average error of around 2.5% outperform alternative forecasting models.This is perhaps explained by the dramatic structural changes seen in the air traffic market

Instrumen kebolehpasaran graduan

Masalah pengangguran dikalangan graduan di Malaysia berada pada tahap yang tidak memuaskan dan perlu diatasi dengan segera.Pelbagai langkah telah diambil oleh kerajaan untuk mengatasi masalah ini termasuklah melaksanakan penilaian kemahiran kebolehpasaran terhadap pelajar IPT melalui instrumen My3S. Langkah ini dilihat sebagai antara langkah yang baik. Bagaimana pun, berdasarkan kaedah penilaian yang dijalankan, kajian ini berpendapat bahawa hasil yang diperolehi tidak akan dapat menilai dengan tepat kemahiran kebolehpasaran yang dimiliki oleh pelajar mahu pun graduan IPT.Kekurangan tersebut cuba diatasi oleh kajian ini melalui pembangunan instrumen yang lebih bersifat“realistik” menggunakan kaedah SJT.Bagaimana pun, sebelum instrumen dibangunkan, perbincangan dilakukan terlebih dahulu berkenaan instrumen kebolehpasaran graduan yang telah wujud di Malaysia.Kemudian, perbincangan dan perbandingan turut dilakukan kepada kemahiran kebolehpasaran yang dikatakan perlu kepada graduan serta kaedah pengukuran instrumen yang kebanyakannya digunakan untuk membuat penilaian.Hal ini bertujuan untuk mendapatkan kemahiran kebolehpasaran yang perlu diuji oleh kajian ini dan bagi membuktikan kelebihan kaedah SJT berbanding kaedah yang lain. Apabila telah dibuktikan, Bab Tiga dibangunkan untuk SJT supaya penerangan yang lebih terperinci dapat diberikan berkenaan kaedah tersebut.Penerangan yang diberikan terdiri daripada lima bahagian iaitu definisi, sejarah SJT, ciri, prosedur pembangunan dan kekuatan SJT. Seterusnya, Instrumen Kebolehpasaran Graduan dibangunkan melalui proses pembangunan instrumen yang disarankan oleh Merten (2005).Bagaimana pun, oleh kerana kaedah SJT terlibat, proses pembangunan instrumen turut merujuk kepada kajian Motowildo et al. (1990) dan Weekley et al. (2006). Seterusnya, instrumen ini dilaksanakan kepada seribu dua ratus orang responden yang terdiri daripada pelajar tempatan tahun akhir UUM dari pelbagai program pengajian. Data yang telah diperolehi dianalisis terlebih dahulu menggunakan kaedah EDA. Kemudian, pemarkahan dilakukan dan analisis diteruskan dengan ujian hipotesis. Berikutnya skor norma dibangunkan melalui kaedah Simulasi Persampelan BCA Bootstrap.Hasil kajian berjaya menunjukkan tahap kemahiran kebolehpasaran yang dimiliki oleh pelajar tempatan tahun akhir UUM.Daripada hasil kajian tersebut, separuh daripada responden dilihat memiliki kemahiran di tahap yang baik dan memuaskan.Bagaimana pun, hasil bagi Kemahiran Keusahawanan menunjukkan terdapat hanya tiga puluh peratus responden sahaja yang memiliki kemahiran tersebut di tahap yang baik dan memuaskan.Secara tidak langsung, keputusan ini dapat memberi gambaran awal kepada pihak UUM untuk memberi fokus untuk meningkatkan Kemahiran Keusahawan pelajar pada masa hadapan.Seterusnya, nilai skor norma juga berjaya diperolehi.Nilai ini boleh digunakan oleh pihak UUM bagi membuat penilaian dan perbandingan kemahiran kebolehpasaran yang dimiliki oleh pelajar tempatan tahun akhir UUM pada masa hadapan

Comparing forecasting effectiveness through air travel data

Airline traffic forecasting in the medium term is important to airlines and regulatory authorities that attempt to plan and schedule capacity. This study examines a number of alternative approaches to forecasting short to medium term (1 to 3 years) air traffic flows. The data examined are flows between the UK and six other countries over the period of 1961- 2002, which has seen substantial changes in both transport technology and economic development. The economic drivers, under consideration, are price, income and bilateral trade. The forecasting models employed include autoregressive models, autoregressive distributed lag models specified using various statistical and economic criteria and a newly developed automatic method for model specification(PcGets), as well as time varying parameter models.Various approaches to including interactions between the contemporaneous air trriffic flows are examined including pooled autoregressive distributed lag models and the inclusion of a 'world' variable that measures overall trade growth in the world economy. Based on the analysis of forecasting error measures, it is concluded that time varying parameter models that include the 'world' variable with an average error of around 2.5% outperform alternative forecasting models. This is perhaps explained by the dramatic structural changes seen in the air traffic market

COMPARING PRICES OF BASIC NEEDS (FOODS AND HOUSES): A CASE STUDY OF CHANGLUN, KODIANG AND JITRA

Recently, the price of goods and services including the basic needs (foods and houses) in Malaysia are increasing slightly. Based on random interviews, there are complaints from low level income community of Changlun claiming that the price of basic needs especially foods and houses in Changlun are more expensive than Kodiang and Jitra. The purpose of this community based study is to investigate the claim of the low level income community whom are majority in Changlun. An observational study was conducted for 6 weeks by collecting actual prices of basic needs (foods and houses) in Changlun, Kodiang and Jitra. Exploratory Data Analysis (EDA) was used to compare the prices. The findings indicated that there exist price disparity of basic needs among Changlun, Kodiang and Jitra. Based on the samples taken, Changlun has the highest prices for foods. However, the prices were still within the price range of Kementerian Perdagangan Dalam Negeri, Koperasi dan Kepenggunaan (KPDNKK). Changlun also has the highest house price with the price disparity of RM18,000 and RM90,000 as compared to Jitra and Kodiang respectively. Further investigations needed to collect more data to generalise this issue and before actions can be taken to assist the low level income community in Changlun to cope with the price hike and survive day to day basis.Keywords: Basic needs, prices, communit

Mixture model of the Exponential, Gamma and Weibull distributions to analyse heterogeneous survival data

Aims: In this study a survival mixture model of three components is considered to analyse survival data of heterogeneous nature.The survival mixture model is of the Exponential, Gamma and Weibull distributions.Methodology: The proposed model was investigated and the Maximum Likelihood (ML) estimators of the parameters of the model were evaluated by the application of the Expectation Maximization Algorithm (EM).Graphs, log likelihood (LL) and the Akaike Information Criterion (AIC) were used to compare the proposed model with the pure classical parametric survival models corresponding to each component using real survival data.The model was compared with the survival mixture models corresponding to each component.Results: The graphs, LL and AIC values showed that the proposed model fits the real data better than the pure classical survival models corresponding to each component.Also the proposed model fits the real data better than the survival mixture models corresponding to each component. Conclusion: The proposed model showed that survival mixture models are flexible and maintain the features of the pure classical survival model and are better option for modelling heterogeneous survival data

Modeling the asymmetric in conditional variance

The purpose of this study is to model the asymmetric in conditional variance of Exponential Generalized Autoregressive Conditional Heteroscedasticity (EGARCH) with Combine White Noise (CWN) model to obtain suitable results. Combine white noise has the minimum information criteria and high log likelihood when compare with EGARCH estimation.The determinant of the residual covariance matrixvalue indicates that CWN estimation is efficient. Combine white noise has minimum information criteria and high log likelihood value that signify suitable estimation. Combine white noise has a minimum forecast errors which indicates forecast accuracy.Combine white noise estimation results have proved more efficient when compared with EGARCH model estimatio

Algorithmic approaches in model selection of the air passengers flows data

Algorithm is an important element in any problem solving situation.In statistical modelling strategy, the algorithm provides a step by step process in model building, model testing, choosing the ‘best’ model and even forecasting using the chosen model.Tacit knowledge has contributed to the existence of a huge variability in manual modelling process especially between expert and non-expert modellers.Many algorithms (automated model selection) have been developed to bridge the gap either through single or multiple equation modelling.This study aims to evaluate the forecasting performances of several selected algorithms on air passengers flow data based on Root Mean Square Error (RMSE) and Geometric Root Mean Square Error (GRMSE).The findings show that multiple models selection performed well in one and two step-ahead forecast but was outperformed by single model in three step-ahead forecasts

Assessing the simulation performances of multiple model selection algorithm

The Autometrics is an algorithm for single equation model selection.It is a hybrid method which combines expanding and contracting search techniques.In this study, the algorithm is extended for multiple equations modelling known as SURE-Autometrics.The aim of this paper is to assess the performance of the extended algorithm using various simulation experiment conditions. The capability of the algorithm in finding the true specification of multiple models is measured by the percentage of simulation outcomes.Overall results show that the algorithm has performed well for a model with two equations.The findings also indicated that the number of variables in the true models affect the algorithm performances. Hence, this study suggests improvement on the algorithm development for future research