Open Access Original Research Article

Additive Seasonality in Time Series using Row and Overall Sample Variances of the Buys-Ballot Table

Kelechukwu C. N. Dozie, Stephen O. Ihekuna

Asian Journal of Probability and Statistics, Page 1-9
DOI: 10.9734/ajpas/2022/v18i330447

This study considers test for seasonality in the additive model using the Buys-Ballot table and the nature of trending curves (linear, quadratic and exponential). The test is applied to the periodic and overall sample variances of the Buys-Ballot table to detect the presence and absence of seasonal indices in time series.

Open Access Original Research Article

Evaluating the Role of Maternal Income in Mediating the Effect of Mother's Education on under Five Child Mortality in Kenya

Irene Mundia, Hellen Waititu, Nelson Owuor, Stanely Sewe

Asian Journal of Probability and Statistics, Page 10-22
DOI: 10.9734/ajpas/2022/v18i330448

Aims/ Objectives: The study identified the role of maternal income in mediating the effect of a mother's education level on UFCM.

Study Design: We sourced secondary data from a 2014 Kenya Health Demographic Health Survey (KHDS). We analyzed data to determine mortality among the under-five children.

Place and Duration of Study: Department of mathematics and Actuarial science, the Catholic University of Eastern Africa, Nairobi, Kenya.

Methodology: We then conducted regression with mediation to assess the effect of a mother's education on UFCM in the presence of a mediator, "mothers income." We also determined the direct, total and indirect effects of the independent variable in the presence of mediation.

Results: The results indicate that maternal education is directly important on UFCM. Maternal education level also channeled its effects through maternal income. Change from no education level to primary education level would reduce the number of deaths by 1.9 deaths per 1000 children. Of this decrease, 0.5 fewer deaths were attributed to the maternal income pathway representing 26 percent of the total effect.

Conclusion: If an intervention could improve, the maternal income of mothers at no education level to that of mothers at higher education level while keeping the other aspects of social deprivation constant we could eliminate 26% of the education level effect.

Open Access Original Research Article

Estimation of Parameters and Optimality of Second-Order Spherical Designs Using Quadratic Function Relative to Non-Spherical Face centered CCD

Onu, Obineke Henry, Ijomah, Maxwell Azubuike, Osahogulu, Dele Joshua

Asian Journal of Probability and Statistics, Page 23-37
DOI: 10.9734/ajpas/2022/v18i330449

The study presented the estimation of parameters and optimality of second-order spherical designs using quadratic model in comparison to the non-spherical face centered CCD for varying axial distances. The designs considered were equiradial design of axial distances of 1.0 and 1.414, inscribed CCD of axial distance of 1.0 and circumscribed CCD of axial distance of 1.414, the study employed sum of square error, variance estimation, D-, A-, and T-optimality criteria as well as Grand mean of these designs for quadratic model and 1 to 10 center runs were considered. The study observed that the sum of square error of the non-spherical face centred CCD is zero (0) for radial point of n=5 with 1 centre point and this result is seen to be a misleading result, because, no process is 100%. While the sum of square error of the spherical designs with axial distance of 1.0 gave minimal sum of square errors and the spherical designs with axial distance of 1.414 gave very large sum of square error. The Grand mean of the spherical and the non-spherical designs were equal or approximately equal for radial point of n=5 for centre points 1-10 inclusive. But as the radial distance increases above 5, the Grand mean of the non-spherical CCD differs significantly from those of the spherical designs. The study suggests that the non-spherical second order design is inferior to their spherical second order design counterparts. The spherical designs with axial distance of 1.414 (equiradial and circumscribed CCD) have better D-optimality, A-optimality and T-optimality than the non-spherical face centred CCD, while, the spherical designs with axial distance of 1.0 (equiradial and inscribed) has inferior D-optimality, A-optimality and T-optimality compared to the non-spherical face centred CCD with axial distance of 1.0.

Open Access Original Research Article

An Investigation into Social and Cultural Pressures of Vulnerable Women using Survival Analysis with Covariates

Oluwafemi S. Oyamakin, Iheanyi Chizaram Emenike

Asian Journal of Probability and Statistics, Page 38-57
DOI: 10.9734/ajpas/2022/v18i330450

In this study, we sought to model the time to the first birth interval from marriage for women in Nigeria, and identify the various factors affecting this timing. The study was also set to determine the average/median survival time for marriage to first birth interval among Nigerian women, to provide enlightenment in such areas and possibly reduce anxiety levels of women who have little or no knowledge of the median survival time to first birth who might be vulnerable to the exploitations of illicit religious and medical practitioners.

Data obtained from the Nigerian Demographic Health Survey (NDHS) 2018 was used for the purpose of this research. Information on the following variables was obtained: Time to first birth from marriage, Age Women's education, Wealth index, Place of residence, Employment, Contraceptive, Religion, and Region. The Kaplan-Meier estimator was used to estimate the median survival time, while the log-rank test was used to test the significance of the categories of the covariates used. The Density, Quantile, Survival and Probability plots were used to study candidate distributions that appropriately describe the data, and the Akaike Information Criterion (AIC) was used to select the best distribution for the Accelerated Failure Time Model.

The study found that the median Survival time of marriage to the first birth interval was 20 months. Level of education, religion, region, use of contraceptives and Wealth Index were found to significantly affect marriage to the first birth interval. A log-normal Accelerated Failure Time Model was fit to the data. Women with higher education were found to have a shorter time to first birth interval. Also, women from South-Western Nigeria had shorter marriage to first birth interval than the other regions.

Open Access Original Research Article

Two Sample Test for Censored Data Based on Sub-Sample Medians

. Ayushee, Narinder Kumar, Manish Goyal

Asian Journal of Probability and Statistics, Page 58-73
DOI: 10.9734/ajpas/2022/v18i330451

In hypothesis testing, the purpose of two-sample problem is to determine the statistical significance of the difference between two independent populations. This paper proposes a nonparametric test statistic based on U -statistic, useful for two-sample scale problem when dealing with randomly right censored data. Proposed test concentrates on comparing the medians of sub-samples from two populations. A simulation study is given for critical values and power of the proposed test statistic at various sample sizes and considering different lifetime distributions. Asymptotic relative efficiencies show that the proposed test is more efficient in comparison to some existing tests available in literature. A real-life data application is also given.