Ekaette Inyang Enang

The application of calibration in domain estimation with subsampling the non-respondents is the major emphasis of this work. The detrimental impact that result from a researcher’s incapacity to gather data from every elemen-tary unit in a certain demographic or from respondents’ partial or complete unwillingness to supply the necessary information is still a problem in sample surveys. In view of the mentioned problem, this work becomes imperative as it utilizes the concept of calibration in double sampling. In order to increase the accuracy of such estimates by subsampling the non-respondents, it becomes important to close the gap between the loss of survey data and establishing a reliable estimate in the research areas. This formulation is subject to two conditions, when the auxiliary variable is free from non-response (condition A) and when the auxiliary variable is not free from non-response (condition B). And it has been demonstrated that the suggested estimators are unbiased. Two populations from actual data were examined in terms of variance/MSE and percentage relative efficiency (PRE) as part of the empirical study. Ad-ditionally, two non-response scenarios-one with uniform rates and the other with non-uniform rate were taken into account. The findings demonstrated that although the two conditions yield the same population mean estimates, condition A is more efficient than condition B. The cases, on the other hand, produce different estimates of population mean and variance/MSE. Compared to the existing estimators used in this work, the proposed estimator has proven to be more effective in providing accurate estimates of the population mean in the domains. This is evident from the efficiency comparisons and empirical investigations of the proposed estimator and the existing estimators that the proposed estimator are capable of producing efficient estimates in domains of study when subsampling the nonrespondents.

It is well known that the ratio and product estimators have the limitation of having efficiency not exceeding that of the linear regression estimator. This paper develops a new approach to ratio estimation that produces a more precise and efficient ratio estimator that is superior to the regression estimator both in efficiency and biasedness. An empirical study is given.

. General Linear Groups are examples of Topological Groups. In this work, a class of whose trace and determinant are equal is constructed. The proposed class is further endowed with Euclidean topology and shown to be a topological group. A sequence of the constructed and its generalization are also presented.

An alternative ratio estimator is proposed for a finite population mean of a study variable Y in simple random sampling using information on the mean of an auxiliary variable X, which is highly correlated with Y. Expressions for the bias and the mean square error of the proposed estimator are obtained. Both analytical and numerical comparisons have shown the proposed alternative estimator to be more efficient than some existing ones. The bias of the proposed estimator is also found to be negligible for all populations considered, indicating that the estimator is as good as the regression estimator and better than the other estimators under consideration.

In this paper, an alternative class of estimators in probability proportional to size (pps) with replacement sampling scheme for multi- character surveys in which the study variables are poorly correlated with selection probabilities is developed. This is achieved by redefining the selection probabilities. Some existing estimators have been shown to be special cases of the proposed class. Numerical illustrations show that some transformations from the proposed class are more efficient than existing estimators under a super-population model.

Alternative Goodness-of-Fit Test in Logistic Regression Models

This study is a cross-cultural investigation of the impact of Nigerian women’s timing of marriage on their marital stability. Gross nuptiality tables and multiple decrement nuptiality tables are constructed based on census data, to examine the regional variations in the nuptiality patterns of Nigerian women across the six geo-political zones in the country. Methodological aspects of the model used in constructing the multiple decrement nuptiality was based on the assumption that re-entrants into marital union is not allowed. The results indicate that girl-child marriage and later-marriage increase the risk of marital dissolution. Various recommendations for policy interventions aimed at improving the marital stability of Nigerian women are stated. KEYWORDS: Marital disruption, Gross nuptiality table, Multiple decrement table, Girl-child marriage, Nuptiality pattern.

Another method of identification of impulse response function in a transfer function is proposed. This method parameterised the transfer function model into a dynamic system model involving right and left model parameters. The right and left parameters of the models are estimated by applying the iterative multiple regression approach on the input and output processes respectively. Results obtained are comparable to those obtained from direct application of the iterative multiple regression on the input process. Global Journal of Mathematical Sciences Vol. 7 (1) 2008: pp. 21-28