

Articles
by
Noor Akma Ibrahim 
Total Records (
6 ) for
Noor Akma Ibrahim 





Rafia Afroz
,
Mohd Nasir Hassan
,
Muhamad Awang
and
Noor Akma Ibrahim


This research employed contingent valuation method (CVM) to estimate the willingness to pay (WTP) of the respondents to improve the air quality in Klang Valley. The samples were divided according to different question formats i.e. open ended(OE), dichotomous choice(DC) and payment card(PC). The objective of this study is to investigate the convergent validity of contingent valuation estimates by comparing the WTP values of different question formats. The comparison of responses to different question formats in terms of positive response rate, valid zero, rejection of contingent market was carried out using the ztests. Paired ttests of equivalent means were also conducted to test the equality of the mean value of the WTP of the respondents for different question formats. The results of the study suggested that the WTP values of the respondents do not differ significantly across different question formats and the WTP values of the respondents using the DC format were the highest. However due to the nature of the question format, the mean WTP values using the DC method would normally be higher than those of OE and PC. The aggregate WTP value of the respondents was RM0.91 billion for air quality improvement in Klang Valley. 





Al Omari Mohammed Ahmed
and
Noor Akma Ibrahim


As the most useful distribution for modeling and analyzing life time data in the medical, paramedical and applied sciences among others, Weibull distribution stands out. Nowadays great attention has been given to Bayesian approach and is in contention with other estimation methods. This study explores and compares the performance of Maximum Likelihood and Bayesian using Jeffrey prior and the extension of Jeffrey prior information for estimating the survival function of Weibull distribution with right censored data. On the performance of these estimators with respect to the mean square error and mean percentage error, comparisons are made through simulation study. For all the varying sample size, several specific values of the scale parameter of the Weibull distribution and for the values given for the extension of Jeffrey prior, the estimate of survival function of maximum likelihood is the best compared to the others when the value of extension of Jeffrey prior is 0.4. But then, extension of Jeffrey prior result is the best compared to others when the value of extension of Jeffrey is 1.4. 




Bader Ahmad I. Aljawadi
,
Mohd Rizam A. Bakar
,
Noor Akma Ibrahim
and
Habshah Midi


In population based cancer clinical trials, a proportion of patients will never experience the interested event and considered as “cured” or “immunes”. The majority of recent cancer studies focus on the estimation of immune proportion. In this study we investigated the estimation of proportion of patients curd of cancer in case of left censored data based on the Bounded Cumulative Hazard (BCH) model proposed by Chen in 1999. The analysis provided the Maximum Likelihood Estimation (MLE) of the parameters within the framework of the Expectation Maximization (EM) algorithm where the numerical solutions of the estimation equations of the cure rate parameter could be employed. 




Al Omari Mohammed Ahmed
,
Noor Akma Ibrahim
,
Mohd Bakri Adam
and
Jayanthi Arasan


We consider the Weibull distribution which has been extensively
used in life testing and reliability studies of the strength of materials. The
maximum likelihood method is the usual frequentist approach in the parameter
estimate for parametric survival data. In this study, we divert from this platform
and use the Bayesian paradigm instead. The Jeffreys and extension of Jeffreys
prior with the squared loss function are considered in the estimation. The Bayes
estimates of the survival function and hazard rate of the Weibull distribution
with censored data obtained using Lindley’s approximation are then compared
to its maximum likelihood counterparts. The comparison criteria is the Mean
Square Error (MSE) and the performance of these three estimates are assessed
using simulations considering various sample sizes, several specific values
of Weibull parameters and several values of extension of Jeffreys prior. The
maximum likelihood estimates of survival function and hazard rate are more efficient
than their Bayesian counterparts, however, the extension of Jeffreys is better
than the maximum likelihood for certain conditions. 





Alireza Bahiraie
,
Noor Akma Ibrahim
,
A.K.M. Azhar
and
Ismail Bin Mohd


Problem statement: Some methodological problems concerning financial ratios such as nonproportionality, nonasymetricity, nonsalacity were solved in this study and we presented a complementary technique for empirical analysis of financial ratios and bankruptcy risk. This new method would be a general methodological guideline associated with financial data and bankruptcy risk. Approach: We proposed the use of a new measure of risk, the Share Risk (SR) measure. We provided evidence of the extent to which changes in values of this index are associated with changes in each axis values and how this may alter our economic interpretation of changes in the patterns and directions. Our simple methodology provided a geometric illustration of the new proposed risk measure and transformation behavior. This study also employed Robust logit method, which extends the logit model by considering outlier. Results: Results showed new SR method obtained better numerical results in compare to common ratios approach. With respect to accuracy results, Logistic and Robust Logistic Regression Analysis illustrated that this new transformation (SR) produced more accurate prediction statistically and can be used as an alternative for common ratios. Additionally, robust logit model outperforms logit model in both approaches and was substantially superior to the logit method in predictions to assess sample forecast performances and regressions. Conclusion/Recommendations: This study presented a new perspective on the study of firm financial statement and bankruptcy. In this study, a new dimension to risk measurement and data representation with the advent of the Share Risk method (SR) was proposed. With respect to forecast results, robust loigt method was substantially superior to the logit method. It was strongly suggested the use of SR methodology for ratio analysis, which provided a conceptual and complimentary methodological solution to many problems associated with the use of ratios. Respectively, robust logit regression can be employed as a tool of regression in providing regression for studies associated with financial data. 




Rafida M. Elobaid
,
Mahendran Shitan
,
Noor Akma Ibrahim
,
Awang N.A. Ghani
and
Daud


Problem statement: Spatial modeling has many applications in various fields like agriculture, meteorology, forestry and it takes into consideration the spatial correlation structures. In the field of forestry the growth rate, in particular, the diameter of trees is usually an important parameter. The growth rate of trees in a forest is likely to be influenced by various factors like nutrients, fertility of soil, sunshine and rainfall. In this study, we investigated the spatial correlation of the mean diameter of trees in the natural Dipterocarp forest in Gunung Tebu forest reserve, Terengganu, Malaysia. Approach: The diameters were measured using the diameter tape and the unit of measurement is in centimeters (cm). The main sampling unit was 1 ha plot of 100 by 100 m located approximately in the centre of each treatment block. Within the 1 ha sample plot, the quadrants (20 by 20 m) were numbered consecutively from 125 and in the outer 16 quadrants; all trees having a diameter at breast height over bark (dbh) of 15.0 cm or more are individually numbered, tagged and enumerated. Using the rook’s and queen’s neighborhood structure, we computed the Moran’s spatial correlation coefficient for the mean diameter of trees in each quadrant for the years 1975 up to 1986. Results: We found that there was a negative spatial correlation among the mean diameter of trees in the 16 quadrants (cases) of the natural Dipterocarp forest in Gunung Tebu forest reserve, Terengganu at α level 0.10. Conclusion/Recommendations: The existence of negative spatial correlation indicated that there was competition among the trees in Dipterocarp forest as a result of tree growth over time which was affected by species, size, age and other environmental factors. Further research will concentrate on the spatial modeling of diameter of trees for the years where negative correlation was found. 





