Statistics
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Vasudeva, R.; Divanji, G. (Society for Industrial and Applied Mathematics, http://epubs.siam.org, NaN, 2006)[more][less]
Abstract: Let (X(t), t ≥ (0) with X(0) = 0 be a stable subordinator with index 0 < α < 1 and let (tk) be an increasing sequence such that tk+1/tk → ∞ as k → ∞. Let (at) be a positive nondecreasing function of t such that a(t)/t 1. Define Y (t) = X(t + a(t)) − X(t) and Z(t) = X(t) − X(t − a(t)), t > 0. We obtain law-of-the-iterated-logarithm results for (X(tk)), (Y (tk)) and Z(tk), properly normalized. URI: http://hdl.handle.net/10311/1135 Files in this item: 1
Divanji_TPA_2006.pdf (120.0Kb) -
Mokgatlhe, L.; Groenewald, P.C.N. (Elsevier, http://www.elsevier.com, NaN, 2005)[more][less]
Abstract: A method for the simulation of samples from the exact posterior distributions of the parameters in logistic regression is proposed. It is based on the principle of data augmentation and a latent variable is introduced, similar to the approach of Albert and chib (J. Am. Stat. Assoc. 88 (1993) 669), who applied it to the probit model. In general, the full conditional distributions are intractable, but with the introductions of the latent variable all conditional distributions are uniform, and the Gibbs sampler is easily applicable. Marginal likelihoods for model selection can be obtained at the expense of additional Gibbs cycles. The technique is extended and can be applied with nominal or ordinal polychotomous data. URI: http://hdl.handle.net/10311/1127 Files in this item: 1
Mokgatlhe_CSDA_2005.pdf (564.2Kb) -
Amey, KA.A.; Forcheh, N.; Setlhare, K. (Dove Medical Press Ltd. www.dovepress.com/, NaN, 2012)[more][less]
Abstract: Background: Predictive models for mortality due to human immunodeficiency virus (HIV) disease as a result of opportunistic infections, such as tuberculosis and pneumonia, have been developed. Methods: The data are taken from the Statistics South Africa multiple causes of death data for 2006 and 2007, which is available for public use. The dataset was compiled from death notifications, and contains up to five causes of death as well as some demographic characteristics of the deceased. The logistic regression modeling framework was used to model the presence or absence of HIV disease, given the predictive variables. Results: The higher the number of causes listed, the higher the likelihood that HIV would be a cause, with the percentage of notifications of HIV listed increasing from under 2% when only one cause is listed to almost 15% when 4–5 causes are listed. When the logit model was fitted to the multiple cause of death model, it was found that individual demographics were good predictors of the likelihood that the death notification would have HIV as one of the causes of death. Although there are highly significant differences in the likelihood that people of different demographics would die from HIV, the predictive power of these demographic factors on their own is very low, especially when there is only a single cause of death mentioned. With the full multiple cause of death model, two-way interactions between tuberculosis, pneumonia, and other opportunistic infections were highly significant, and their inclusion lead to significant improvements in the predictive power of the model. URI: http://hdl.handle.net/10311/1071 Files in this item: 1
Forcheh_OAMS_2012.pdf (302.7Kb) -
Ama, N.O.; Oucho, J.O. (Medical and Pharmaceutical Publications, NaN, 2009)[more][less]
Abstract: Background: The healthcare of Batswana (citizens of Botswana) as indicated in the country’s Vision 2016 is one of the top priorities of the government of Botswana, yet Botswana’s National Health Policy, the Immigration Policy and the National Sexual and Reproductive Health Programme Framework all are silent on the obligations of the government to provide health services to the immigrant and refugee population. In view of the high prevalence of HIV/AIDS in Botswana, South Africa and other sub-Saharan countries, it is critical that reproductive health services be as affordable and accessible for the immigrants and refugees as they are for other residents in Botswana. This study measured the views of the primary healthcare providers in Botswana on the perceived reproductive health needs of immigrants and refugees and the availability and accessibility of reproductive healthcare services to the immigrant and refugee populations in the country. This information will be important for policy makers, the government of Botswana and the private sector to shape intervention measures to assist immigrants and refugees in seeking and accessing the desired reproductive health services. Methods: The study targeted all 4 667 medical doctors and nurses who were serving in various hospitals and clinics in 23 health districts of Botswana as at June 2005 when this study was conducted. Using NCS Pearson statistical software, the sample size for the study was determined to be 851. This estimated sample size was allocated to the 23 health districts (strata) using probability proportional to size (PPS). Having obtained the sample size for each district, the healthcare providers to be interviewed from each health district were selected randomly and in proportion to the number of doctors and nurses in each district. Questionnaires were administered to these healthcare providers by research assistants who explained the purpose of the study and obtained informed consent. The questionnaires were coded to ensure the anonymity of the respondents. It contained questions about the healthcare providers’ demographic characteristics, their opinions on the reproductive health needs of immigrants and refugees, and their views on factors that influence the accessibility of these services to immigrants and refugees. Data were collected from 678 doctors and nurses(about 80% of the targeted sample). Results: The majority of the healthcare providers indicated that the most important reproductive health needs of the immigrants and refugees, namely pregnancy-related services (prenatal, obstetrics, postnatal conditions), treatment for sexually transmitted infections (STIs), HIV/AIDS treatment and counselling and family planning were not different from those of the locals. However, some major differences noted between the local population and the foreigners were (i) that antiretroviral (ARV) treatment and prevention of mother-to-child-transmission (PMTCT) programmes were never accessible to the non-citizens; and (ii) that while treatments and other health services were free to Batswana, a fee was charged to non-citizens. Although 86% of the 21 studied reproductive health services were available in the healthcare system more than 50% of the time, only 62% of them were accessible to the immigrants and refugees 50% of the time. The major reasons for inability to access these services were: (i) The immigrants and refugees have to pay higher fees to access the reproductive health services; (ii) Once an immigrant or refugee is identified as HIV positive, there are no further follow-ups on the patient such as detecting the immune status using a CD4 count or testing the viral load; (iii) The immigrants and refugees do not have referral rights to referral clinics/hospitals for follow-ups in case of certain health conditions; and (iv) The immigrants and refugees are required to join a medical aid scheme to help offset part of the costs for the desired services. Conclusions: The study recommended that the government of Botswana should improve the availability of reproductive health services to immigrants and refugees, and expunge those laws and practices that make it difficult for immigrants and refugees to access the available reproductive health services. URI: http://hdl.handle.net/10311/1070 Files in this item: 1
Ama_SAFP_2009.pdf (664.2Kb) -
Forcheh, N. (Wiley-Blackwell, www.wiley.com/wiley-blackwell, NaN, 2002)[more][less]
Abstract: Summary. Ehrenberg presented the simple law-like relationship log(w) = 0.8h + 0.4 ? 0.04 between the weight and height of children aged 5-13 years. Several researchers have confirmed that this relationship holds, irrespective of the child's ethnic, racial, gender and social class. In anthropometry, a weight-height relationship is used to measure the nutritional status of children. For this purpose, the World Health Organization have adopted the National Center for Health Statistics population as the international reference population. The relationship between the World Health Organization-National Center for Health Statistics anthropometric standards and Ehrenberg law-like relationship is examined. Differences between the weight-for-height relationship in anthropometry and the law-like relationship between weight and height for children are small and can be attributable to functional differences. It is found that an Ehrenberg law-like relationship can be extended to include children who are under 5 years old. Criteria for using the law-like relationship to assess the nutritional status of these children are thus suggested. The criteria are evaluated using anthropometric data of a sample of 513 children from a rural district of Botswana. The results indicate that the proposed method of using the law-like relationship to assess nutritional status is much simpler and at least as reliable as the existing methods in anthropometry. Description: Symbols on the abstract may differ from the original abstract URI: http://hdl.handle.net/10311/1055 Files in this item: 1
Forcheh_JRSS.A_2002.pdf (2.588Mb)