Suzilah Ismail

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.

A new approach in measuring graduate employability skills

Globalization makes graduate recruitment for an organization becomes more complex because employers believe that a holistic workforce is the key success of an organization. Currently, although graduates are said to possess specific skills but they still lack of employability skills, and this lead to increment of training cost either by government or even employers. Therefore, graduate level of employability skills should be evaluated before entering work market. In this study, a valid and reliable instrument embedding a new approach of measuring employability skills was developed using Situational Judgment Test (SJT). The instrument comprises of twelve (12) items measuring communication skill, professional ethics and morality, entrepreneurial skill, critical thinking in problem solving and personal quality. Instrument’s validity was achieved through expert opinion and the reliability (in terms of stability) was based on the Chi-Square for homogeneity test. Generally, the instrument is beneficial to graduates, employers, government agencies, university, and workforce recruitment agencies when evaluating the level of employability skills.Globalization makes graduate recruitment for an organization becomes more complex because employers believe that a holistic workforce is the key success of an organization. Currently, although graduates are said to possess specific skills but they still lack of employability skills, and this lead to increment of training cost either by government or even employers. Therefore, graduate level of employability skills should be evaluated before entering work market. In this study, a valid and reliable instrument embedding a new approach of measuring employability skills was developed using Situational Judgment Test (SJT). The instrument comprises of twelve (12) items measuring communication skill, professional ethics and morality, entrepreneurial skill, critical thinking in problem solving and personal quality. Instrument’s validity was achieved through expert opinion and the reliability (in terms of stability) was based on the Chi-Square for homogeneity test. Generally, the instrument is beneficial to gradua...

A Parametric Mixture Model of Three Different Distributions: An Approach to Analyse Heterogeneous Survival Data

A parametric mixture model of three different distributions is proposed to analyse heterogeneous survival data. The maximum likelihood estimators of the postulated parametric mixture model are estimated by applying an Expectation Maximization Algorithm (EM) scheme. The simulations are performed by generating data, sampled from a population of three component parametric mixture of three different distributions. The parameters estimated by the proposed EM Algorithm scheme are close to the parameters of the postulated model. To investigate the consistency and stability of the EM scheme, the simulations are repeated several times. The repetitions of the simulation gave parameters closer to the values of postulated models, with relatively small standard errors. Log likelihood, AIC and BIC are computed to compare the proposed mixture model with parametric mixture models of one distribution. The calculated values of Log likelihood, AIC and BIC are all in favour of the proposed parametric mixture model of different distributions.

MANOVA versus alternative methods

Multivariate analysis of variance (MANOVA) is a powerful tool in analysing multivariate data of multi-factorial experiments. However one of the assumptions in MANOVA requires the data to be normally distributed. This study concerned with the violation of this assumption, particularly when the data are either moderately non-normal or extremely non-normal. Possible alternative methods of handling such data are (i) permutational MANOVA (PMANOVA) or (ii) analysis of distance (AoD). Both of these alternative methods were compared with MANOVA via Monte Carlo experiments using the power of tests. The experiments focussed on testing interaction effects by incorporating different data types (i.e. having multivariate normal distribution, moderately non-normal and extremely non-normal), three level of inter-variable correlations (low: 0.25, medium: 0.5 and high: 0.75), two designs (small: 3×3 and large: 7×7) and two sample sizes (2 and 5 replicates). Overall, the results revealed that irrespective of the data types ...

The impact of 2008 credit crisis on currency stability structure

The depreciation of many currencies over the world has retarded the economic development during 2008 credit crisis. The aim of this study is to detect the existence of changes in the currency stability structure by using a new covariance structure test known as S* statistics for high dimensional data involving 74 currencies. Comparisons were made between monthly data and overall data of 2008. Further analysis was conducted using network topology to visualise the pattern of structural changes and identifying which currencies affected by the crisis. The findings disclose that October currency structure has the utmost changes as compared to overall structure 2008. Forty one (or 55%) currencies were affected. The most affected currencies were Austrian schilling (ATS) and followed by Lebanese pound (LBP) and Mexican peso (MXN). These findings reflect the major impact of 2008 credit crisis on deterioration currencies performance.

Basic needs of Universiti Utara Malaysia students

Basic needs are defined as goods or services that are essential for human to live and function. Wants on the other hand, are goods or services that are not necessary but we desire or wish for in order to fulfil our needs. In university, students’ needs and wants are not always easily detectable due to different generations of students. The students’ desires are also caused by peer interactions, course needs and cultural differences. For example older generations requires typewriter but new generations need a laptop. Many university students have difficulty to differentiate between basic needs and wants. This leads to financial management problem which can affect their academic performance. The purpose of this study is to identify students of Universiti Utara Malaysia (UUM) basic needs. Based on past studies conducted by 3 universities, 12 items related to students’ basic needs were identified. However, only 9 items are considered relevant to UUM students. A study on a focus group consist of 18 students fr...

Performance of fuzzy approach in Malaysia short-term electricity load forecasting

Many activities such as economic, education and manafucturing would paralyse with limited supply of electricity but surplus contribute to high operating cost. Therefore electricity load forecasting is important in order to avoid shortage or excess. Previous finding showed festive celebration has effect on short-term electricity load forecasting. Being a multi culture country Malaysia has many major festive celebrations such as Eidul Fitri, Chinese New Year and Deepavali but they are moving holidays due to non-fixed dates on the Gregorian calendar. This study emphasis on the performance of fuzzy approach in forecasting electricity load when considering the presence of moving holidays. Autoregressive Distributed Lag model was estimated using simulated data by including model simplification concept (manual or automatic), day types (weekdays or weekend), public holidays and lags of electricity load. The result indicated that day types, public holidays and several lags of electricity load were significant in t...

Computational efficiency of generalized variance and vector variance

In multivariate statistical quality control, the existing tests known as Generalized Variance (GV) and Vector Variance (VV), plays an important role in measuring process variability. In this paper, we present the computational efficiency of both tests to illustrate that their complexity as a function of dimension. From the mathematical derivation and simulation study, the computational efficiency of VV outperforms GV, particularly when the number of variables is large.

Univariate time series forecasting algorithm validation

Forecasting is a complex process which requires expert tacit knowledge in producing accurate forecast values. This complexity contributes to the gaps between end users and expert. Automating this process by using algorithm can act as a bridge between them. Algorithm is a well-defined rule for solving a problem. In this study a univariate time series forecasting algorithm was developed in JAVA and validated using SPSS and Excel. Two set of simulated data (yearly and non-yearly); several univariate forecasting techniques (i.e. Moving Average, Decomposition, Exponential Smoothing, Time Series Regressions and ARIMA) and recent forecasting process (such as data partition, several error measures, recursive evaluation and etc.) were employed. Successfully, the results of the algorithm tally with the results of SPSS and Excel. This algorithm will not just benefit forecaster but also end users that lacking in depth knowledge of forecasting process.

Implementation of Graduate Employability Skills SJT Instrument in Universiti Utara Malaysia

Assessing graduate employability skills before they enter the job market is very important because if they are lacking certain skills, improvement can be made through the process of training. In this study, a valid and reliable new instrument for measuring graduate employability skills using Situational Judgement Test (SJT) approach was implemented. The instrument consisted of 12 items representing five employability skills namely communication skill, professional ethics & morality, entrepreneurial skill, critical thinking in problem solving and personal quality. The purpose was to obtain a norm score for each of these skills. A survey was conducted using the SJT instrument on 1012 Universiti Utara Malaysia (UUM) local undergraduate final year students. The norm score was generated by employing BCA bootstrap technique. Scores guideline was created based on three levels (low, moderate and high). The outcomes indicated that the students possessed moderate level of communicationskill, entrepreneurial skill, ...