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Search Results: 1 - 10 of 11415 matches for " George Otieno Orwa "
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Estimation of Population Variance Using the Coefficient of Kurtosis and Median of an Auxiliary Variable under Simple Random Sampling  [PDF]
Tonui Kiplangat Milton, Romanus Otieno Odhiambo, George Otieno Orwa
Open Journal of Statistics (OJS) , 2017, DOI: 10.4236/ojs.2017.76066
Abstract:

In this study we have proposed a modified ratio type estimator for population variance of the study variable y under simple random sampling without replacement making use of coefficient of kurtosis and median of an auxiliary variable x. The estimator’s properties have been derived up to first order of Taylor’s series expansion. The efficiency conditions derived theoretically under which the proposed estimator performs better than existing estimators. Empirical studies have been done using real populations to demonstrate the performance of the developed estimator in comparison with the existing estimators. The proposed estimator as illustrated by the empirical studies performs better than the existing estimators under some specified conditions i.e. it has the smallest Mean Squared Error and the highest Percentage Relative Efficiency. The developed estimator therefore is suitable to be applied to situations in which the variable of interest has a positive correlation with the auxiliary variable.

NONPARAMETRIC MIXED RATIO ESTIMATOR FOR A FINITE POPULATION TOTAL IN STRATIFIED SAMPLING
George Otieno Orwa,Romanus Odhiambo Otieno,Peter Nyamuhanga Mwita
Pakistan Journal of Statistics and Operation Research , 2010, DOI: 10.1234/pjsor.v6i1.149
Abstract: We propose a nonparametric regression approach to the estimation of a finite population total in model based frameworks in the case of stratified sampling. Similar work has been done, by Nadaraya and Watson (1964), Hansen et al (1983), and Breidt and Opsomer (2000). Our point of departure from these works is at selection of the sampling weights within every stratum, where we treat the individual strata as compact Abelian groups and demonstrate that the resulting proposed estimator is easier to compute. We also make use of mixed ratios but this time not in the contexts of simple random sampling or two stage cluster sampling, but in stratified sampling schemes, where a void still exists.
GENERALISED MODEL BASED CONFIDENCE INTERVALS IN TWO STAGE CLUSTER SAMPLING
Christopher Ouma Onyango,Romanus Odhiambo Otieno,George Otieno Orwa
Pakistan Journal of Statistics and Operation Research , 2010, DOI: 10.1234/pjsor.v6i2.128
Abstract: Chambers and Dorfman (2002) constructed bootstrap confidence intervals in model based estimation for finite population totals assuming that auxiliary values are available throughout a target population and that the auxiliary values are independent. They also assumed that the cluster sizes are known throughout the target population. We now extend to two stage sampling in which the cluster sizes are known only for the sampled clusters, and we therefore predict the unobserved part of the population total. Jan and Elinor (2008) have done similar work, but unlike them, we use a general model, in which the auxiliary values are not necessarily independent. We demonstrate that the asymptotic properties of our proposed estimator and its coverage rates are better than those constructed under the model assisted local polynomial regression model.
Multivariate Ratio Estimator of the Population Total under Stratified Random Sampling  [PDF]
Oscar O. Ngesa, G. O. Orwa, R. O. Otieno, H. M. Murray
Open Journal of Statistics (OJS) , 2012, DOI: 10.4236/ojs.2012.23036
Abstract: Olkin [1] proposed a ratio estimator considering p auxiliary variables under simple random sampling. As is expected, Simple Random Sampling comes with relatively low levels of precision especially with regard to the fact that its variance is greatest amongst all the sampling schemes. We extend this to stratified random sampling and we consider a case where the strata have varying weights. We have proposed a Multivariate Ratio Estimator for the population mean in the presence of two auxiliary variables under Stratified Random Sampling with L strata. Based on an empirical study with simulations in R statistical software, the proposed estimator was found to have a smaller bias as compared to Olkin’s estimator.
Statistical Models for Forecasting Tourists’ Arrival in Kenya  [PDF]
Albert Orwa Akuno, Michael Oduor Otieno, Charles Wambugu Mwangi, Lawrence Areba Bichanga
Open Journal of Statistics (OJS) , 2015, DOI: 10.4236/ojs.2015.51008
Abstract: In this paper, an attempt has been made to forecast tourists’ arrival using statistical time series modeling techniques—Double Exponential Smoothing and the Auto-Regressive Integrated Moving Average (ARIMA). It is common knowledge that forecasting is very important in making future decisions such as ordering replenishment for an inventory system or increasing the capacity of the available staff in order to meet expected future service delivery. The methodology used is given in Section 2 and the results, discussion and conclusion are given in Section 3. When the forecasts from these models were validated, Double Exponential Smoothing model performed better than the ARIMA model.
Local Polynomial Regression Estimator of the Finite Population Total under Stratified Random Sampling: A Model-Based Approach  [PDF]
Charles K. Syengo, Sarah Pyeye, George O. Orwa, Romanus O. Odhiambo
Open Journal of Statistics (OJS) , 2016, DOI: 10.4236/ojs.2016.66088
Abstract: In this paper, auxiliary information is used to determine an estimator of finite population total using nonparametric regression under stratified random sampling. To achieve this, a model-based approach is adopted by making use of the local polynomial regression estimation to predict the nonsampled values of the survey variable y. The performance of the proposed estimator is investigated against some design-based and model-based regression estimators. The simulation experiments show that the resulting estimator exhibits good properties. Generally, good confidence intervals are seen for the nonparametric regression estimators, and use of the proposed estimator leads to relatively smaller values of RE compared to other estimators.
Longitudinal Survey, Nonmonotone, Nonresponse, Imputation, Nonparametric Regression  [PDF]
Sarah Pyeye, Charles K. Syengo, Leo Odongo, George O. Orwa, Romanus O. Odhiambo
Open Journal of Statistics (OJS) , 2016, DOI: 10.4236/ojs.2016.66092
Abstract: The study focuses on the imputation for the longitudinal survey data which often has nonignorable nonrespondents. Local linear regression is used to impute the missing values and then the estimation of the time-dependent finite populations means. The asymptotic properties (unbiasedness and consistency) of the proposed estimator are investigated. Comparisons between different parametric and nonparametric estimators are performed based on the bootstrap standard deviation, mean square error and percentage relative bias. A simulation study is carried out to determine the best performing estimator of the time-dependent finite population means. The simulation results show that local linear regression estimator yields good properties.
Integration of Ground Magnetics and Energy Dispersive X-Ray Fluorescence Spectroscopy in Ilmenite Prospection in Magaoni, Kenya  [PDF]
George Oduor Otieno, John Gitonga Githiri, Willis Jakanyango Ambusso
Open Journal of Applied Sciences (OJAppS) , 2016, DOI: 10.4236/ojapps.2016.62008
Abstract: The geology of Magaoni area is associated with the presence of heavy minerals [1]. Magaoni’s neighbours Maumba and Nguluku where ilmenite was discovered by Tiomin Resource Inc. in 1996, using drilling and chemical analysis [2]. Ilmenite mineral is known to be magnetically weak, but provides observable magnetic response [3]. In this study, ground magnetic survey method was carried out to map magnetic anomalies of established stations, associated with ilmenite bearing formations. The magnetic contour map plotted showed weak and shallow magnetic signatures spread throughout the study area. 2D Euler deconvolution solutions revealed presence of magnetised formations from near surface to a maximum depth of about 450 m at some points. The weak magnetic formations of near surface indicated presence of ilmenite. Energy dispersive X-ray spectroscopy was done on soil samples collected randomly from the study area to determine the percentage of iron and titanium oxides. The results showed elevated values of titanium dioxide, ranging from 1.5% to 13% which is way above the global average of about 0.7% [4]. The percentage of iron oxide was low, ranging from 1.5% to 4%, this being the reason for weak magnetisation of the study area.
Indigenous Knowledge Used in Breeding and Management of Capra hircus Populations in Kajiado and Makueni Counties, Kenya  [PDF]
Okello George Otieno, Joseph Owino Junga, M. S. Badamana, Joshua O. Amimo
Open Journal of Genetics (OJGen) , 2015, DOI: 10.4236/ojgen.2015.53009
Abstract: The aim of this project was to study indigenous breeding practices used in management of Capra hircus (Galla and Small East African goats) populations in Kajiado County in Rift valley province and Makueni County in Eastern province. Data were obtained through a field survey using questionnaires (Appendix I) and personal observations between 1st September, 2013 and 2nd December, 2013. This study covered key characteristics of goats production and areas of goat breeding, such as general farm details, number of goats, main activities of the farmers, farming types, breeds, flock structure, feeding, housing, catastrophes, selection, mating systems, breeding systems, average age at parturition, breeding problems, and the importance of goats. Results showed that the average number of goats in Kajiado was 100.65 ± std 49.88 while in Makueni it was 12.28 ± std 6.46. The main activity of the people interviewed was farming as 58 people (96.67%) in Kajiado and 42 people (61.60%) chose farming as their main activity because this was their main source of livelihood. Flocks were dominated by breeding females at a mean of 39.06 ± std 16.75 in Kajiado and a mean of 5.62 ± std 3.50 in Makueni because females were kept to reproduce to increase the size of the flock and the males were kept majorly for cash and only one or two were left to reproduce with the females. Drought was the major catastrophe as it killed an average number of goats of 6.33 ± std 4.36. Pneumonia and diarrhoea were the major diseases according to 28 farmers (46.66%) in Kajiado and 31 farmers (51.66%) in Makueni. Ticks and fleas were the major parasites according to 42 farmers (70%) in Kajiado and 4 farmers (63.34%) in Makueni. Treatment was mostly done by the farmers individually as 54 farmers (90%) in Kajiado and 46 farmers (76.67%) in Makueni treated the animals by themselves. This was so because it was either not easy to get a veterinarian or expensive for them to hire veterinarian doctors. Some farmers used traditional medicine like mavuavui; Steganotaenia araliacea was used to treat pneumonia. Farmers also devised feeding methods during drought as 48 farmers (80.00%) in Kajiado and 23 farmers (38.33%) in Makueni cut leaves from up trees to feed the goats. When doing selection of breed, 58 farmers (96.67%) and 57 farmers (95%) considered large body size and drought resistance respectively in Kajiado. The farmers in Makueni considered age and drought resistance at equal chances of 59 farmers (98.33%). The main mating system was naturally uncontrolled as 113
Human Bocavirus Infection in Children with Acute Respiratory Infection in Nairobi, Kenya  [PDF]
Samwel Morris Lifumo Symekher, George Gachara, James Maylor Simwa, Jane Gichogo, Moses Rotich, Musa Otieno Ng’ayo, Japheth Magana
Open Journal of Medical Microbiology (OJMM) , 2013, DOI: 10.4236/ojmm.2013.34035
Abstract: Background: Acute respiratory infection (ARI) is a leading cause of morbidity and mortality in children under five years of age in developing countries with viruses contributing significantly to this problem. The recently identified parvovirus, Human Bocavirus (HBoV), has also been associated with ARI. Objective: To determine the frequency of HBoV in patients with ARI. Materials and Methods: Samples from 125 consenting patients with influenza like illness signs and symptoms were collected. DNA was extracted from these samples using the QIAamp DNA blood mini kit (Qiagen, Germany). Conventional PCR was carried out and the amplicons were examined in 2% agarose gels stained with ethidium bromide. This was followed by sequencing of the HBoV positive samples. Results: Twenty one (16.8%) patients were found to have HBoV infection. Males (n = 61.9%) were mainly infected with HBoV. Local HBoV strains had 98.9% - 100% similarities and were found to cluster together with other strains obtained elsewhere. Conclusion: These findings suggest that HBoV plays a role in respiratory tract infections in children in Kenya just like it has been found elsewhere. It also sheds light on multiple infections associated with HBoV infections in Kenya.
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