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The Comparison of Parameter Estimation with Application to Massachusetts Health Care Panel Study (MHCPS) DataHuang, Yao-wen 03 June 2004 (has links)
In this paper we propose two simple algorithms to estimate parameters £] and baseline survival function in Cox proportional hazard model with application to Massachusetts Health Care Panel Study (MHCPS) (Chappell, 1991) data which is a left truncated and interval censored data. We find that, in the estimation of £] and baseline survival function, Kaplan and Meier algorithm is uniformly better than the Empirical algorithm. Also, Kaplan and Meier algorithm is uniformly more powerful than the Empirical algorithm in testing whether two groups of survival functions are the same. We also define a distance measure D and compare the performance of these two algorithms through £] and D.
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Arbetslivsinriktad rehabilitering för sjukskrivna arbetslösa - funkar det?Bjerkesjö, Johan, Nilsson, Martin January 2006 (has links)
En av de mest debatterade politiska frågorna de senaste åren har varit den påstått kraftiga ökningen av antalet sjukskrivningar. Parallellt med sjukskrivningarna har även antalet förtidspensionärer ökat. En grupp som inte uppmärksammas lika ofta av varken politikerna eller medierna är de människor som både är sjukskrivna och arbetslösa, och det är den gruppen som vår uppsats kommer att kretsa kring. Syftet med denna uppsats är att utvärdera försäkringskassans och arbetsförmedlingens samverkan kring den gemensamma kundgruppen sjukskrivna arbetslösa. Denna samverkan har bedrivits i Uppsala län sedan september 2003. Närmare bestämt avser vi att besvara frågan om det går att påvisa en behandlingseffekt av den arbetslivsinriktade rehabilitering som ges inom ramen för samverkan? Den metod som vi använder oss av i uppsatsen för att testa samverkansprojektet är Kaplan-Meiers product-limit estimator. Material till undersökning kommer från den uppföljningsfil, i vilken försäkringskassans samverkanshandläggare regelbundet för in uppgifter om alla samverkansärenden. Vi kan med våran undersökning inte finna något stöd för att behandlingen har någon effekt för dem som deltar i samverkansprojektet. Begränsningar i materialet gör dock att vi inte vill dra några mer långtgående slutsatser angående effekten. Istället förespråkar vi att det görs ytterligare undersökningar av samverkan kring arbetslösa sjukskrivna.
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Išgyvenamumo statistinė analizė, sergant kraujotakos susirgimais / Survival statistic analyze for being ill confucions of circulatory systemGalčiūtė, Rima 20 June 2006 (has links)
SUMMARY The goal of the present thesis is to ascertain patients functional classes changes of various time after surgery, investigation of the other factors, which may stipulate recovery state (alive or die) and to estimate investigation of other factors, which may stipulate survival time. The investigation was carried out in two stages. During the first stage, the data was accumulated for processing (investigation of the pairwise independence of variables); the second stage implied solution of the statistical tasks (solution of the tasks, which correspond to the goals of the thesis). The methods of data analysis, the model of binary logistic regression, the descriptive methods for survival data and regression model for survival data were applied. 120 patients, who survived the mitral valve incompetence, were investigated and it was ascertained that functional class depends on difficulty of disease. The Sign‘s and Wilcoxon‘s tests assisted us in drawing the conclusion that statistical significance of surgery produce an impact upon the functional class to the 6‘th month and from 2‘th year to the 6‘th year. The model of the binary logistic regression assisted us in drawing the conclusion that functional class, acute disease and operation time produce an impact upon recovery state (alive or die).
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Cox Model Analysis with the Dependently Left Truncated DataLi, Ji 07 August 2010 (has links)
A truncated sample consists of realizations of a pair of random variables (L, T) subject to the constraint that L ≤T. The major study interest with a truncated sample is to find the marginal distributions of L and T. Many studies have been done with the assumption that L and T are independent. We introduce a new way to specify a Cox model for a truncated sample, assuming that the truncation time is a predictor of T, and this causes the dependence between L and T. We develop an algorithm to obtain the adjusted risk sets and use the Kaplan-Meier estimator to estimate the Marginal distribution of L. We further extend our method to more practical situation, in which the Cox model includes other covariates associated with T. Simulation studies have been conducted to investigate the performances of the Cox model and the new estimators.
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Estimation of Hazard Function for Right Truncated DataJiang, Yong 27 April 2011 (has links)
This thesis centers on nonparametric inferences of the cumulative hazard function of a right truncated variable. We present three variance estimators for the Nelson-Aalen estimator of the cumulative hazard function and conduct a simulation study to investigate their performances. A close match between the sampling standard deviation and the estimated standard error is observed when an estimated survival probability is not close to 1. However, the problem of poor tail performance exists due to the limitation of the proposed variance estimators. We further analyze an AIDS blood transfusion sample for which the disease latent time is right truncated. We compute three variance estimators, yielding three sets of confidence intervals. This work provides insights of two-sample tests for right truncated data in the future research.
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The impact of race and language concordance between patients and navigators on time to diagnostic resolution of breast and cervical cancer screening abnormalitiesCharlot, Marjory January 2013 (has links)
BACKGROUND: Patient navigators have been shown to reduce cancer disparities among racial/ethnic minorities by improving timely diagnosis and treatment of cancer. We sought to determine if race/ethnicity and language concordance of patients and their navigator improved time to diagnostic resolution of breast and cervical cancer screening abnormalities.
METHODS: Demographic data on patients and navigators from the Boston Patient Navigation Research Program were used to assess concordance by race, ethnicity, and language. Kaplan-Meier survival curves and Cox proportional hazards regression models examined the association of race/ethnicity and language concordance on time to definitive diagnosis of cancer screening abnormalities. All analyses were performed separately for breast and cervical groups.
RESULTS: There were 1257 patients and 23 navigators in this study. In the breast group (n=655), 44% of patient-navigator pairs were concordant by race/ethnicity and 75% were language concordant. In the cervical group (n=602), 70% of patient-navigator pairs were race/ethnicity concordant and 87% were language concordant. There was no association with race/ethnicity concordance and time to diagnostic resolution for the breast group, aHR 1.19 (95% CI: 0.97, 1.46) or cervical group, aHR 1.23 (95% CI: 0.99, 1.53). However, in the stratified analysis, race/ethnicity concordance was associated with timelier resolution for minority women with breast and cervical cancer screening abnormalities but not for Whites. For cervical cancer screening abnormalities resolving in less than 90 days, language concordance was also associated with timelier resolution, aHR of 1.46 (95% CI: 1.18, 1.80) but there was no association in the breast group. In the subgroup analysis of Spanish concordance there was also an association of timelier resolution for those with cervical cancer screening abnormalities resolving in less than 90 days.
CONCLUSION: Patient-navigator race/ethnicity concordance is associated with timelier diagnostic resolution of breast and cervical cancer screening abnormalities among minority women. Language concordance is also associated with timelier resolution in participants with cervical cancer screening abnormalities despite the availability and use of interpreters. Given poorer cancer outcomes among minority women, the use of patient navigators that are diverse by race/ethnicity and multilingual may help address barriers to care and improve health outcomes among low-income minorities.
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Labor market participation of African immigrants in Sweden, 1995-2008Manhica, Hélio January 2012 (has links)
This study examines the pattern of unemployment duration of African immigrants in Sweden as well as the effect of emigration origin, age, gender, level of education and family characteristics on the probability of getting a job upon arrival. The study is based on PLACE-database; the dataset is restricted to individuals born in Africa who immigrated to Sweden during the period of 1994-2008. Results from the Kaplan–Meier estimators and Proportional Hazard Models indicate that unemployment duration and the relative risk of getting a job upon arrival vary according to emigration origin and gender differences. In fact, immigrants from Somalia experience longer unemployment duration than Sub Saharan and North African immigrants. Additionally, African women are more likely to experience longer unemployment duration in comparison to men. Women from Sub Saharan Africa experience shorter unemployment duration in comparison to Somalis and North African ones. On the contrary, there are North African men who experience shorter unemployment duration than men from Sub- Saharan African and Somalia. The results also indicate that the relative risk of leaving unemployment upon arrival also differ by gender and region of emigration. In fact, men experience higher relative risk of leaving unemployment in comparison to women. In addition, the gender gap is found to be much more remarkable among the North African immigrants in comparison to Somalis and Sub Saharan ones. Furthermore, the possibility of leaving unemployment upon arrival decreases with age and childbearing, moreover holding university education increases the relative risk of leaving unemployment upon arrival.
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Significance of Nondetects in the Mapping of Soil contaminants.Zhang, Hongyu January 2013 (has links)
In the sample data of soil contaminants, the existence of nondetects is a common phenomenon. Due to their small values, they are always ignored. However, they form an essential part of the sample distribution and arbitrary changes of their values will affect the properties of the distribution, for example, the 95% upper confidence limit of the mean (95UCLM), which is an important index in risk assessment, is strongly related with the sample distribution. Statistical analysis methods for nondetects involve substitution by half of the detection limit (DL/2), maximum likelihood estimation (MLE), Kaplan-Meier and regression on ordered statistics (ROS). The significance of nondetects was examined in this study. Two large data sets of cadmium (Cd) and mercury (Hg) containing censored observations in Annedal’s park were used, where the censored observations were known from the laboratory. Large data sets were subsampled into small data sets with different sample sizes and censoring levels. The 95UCLM value of each data set was calculated by use of the statistical software ProUCL 4.1.00. Through comparison, it was found that in most cases the 95UCLM value calculated with lab values was lower than that of the censored observation for each data set. The difference in 95UCLM values between the data set with nondetects and the data set with lab values varied in each sample and was found to be related to sample size and to the censoring level. The higher the censoring level was, the bigger the 95UCLM value difference became. Either too small or too large a sample size would reduce the difference between the 95UCLM values. This result helps in certain cases, when the 95UCLM value of the sample data is a little lower than the threshold; using the lab values instead of nondetects to recalculate the 95UCLM value may supply a manageable and economic tool to classify the contaminated area.
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Determinants of Student Attrition After the Sophomore Year at The University of ToledoJoseph, Carl Henry January 2020 (has links)
No description available.
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The Effects of Social Assistance and Unemployment Insurance on Employment Outcomes : Evidence from new micro level administrative data at Statistics Sweden between 2019-2023Bernhardsson, Molly January 2024 (has links)
In this study, I examine the employment effects on average earnings and duration to work during a 45 month period, after receiving social assistance (SA) in October 2019, compared to receiving unemployment insurance (UI) the same month. A distinction is made between two treatment groups; receiving SA in addition to UI (treatment I) and receiving SA (treatment II). Using propensity score matching (PSM), I estimate the average treatment effects on the treated on earnings, as well as duration to work by using the Kaplan-Meier survival estimator with the matched observations. I use newly released Swedish administrative micro level data of individuals’ monthly labour market status (BAS) between 2020-2023, from Statistics Sweden. During this thesis process, where Statistics Sweden allowed me data access, I was allowed an additional year of data, for 2019. Results showed that the inflow of SA recipients in October 2019, on average had 25.5 percent lower earnings between November 2019-July 2023, compared to the inflow of UI recipients the same month. In addition, the inflow of SA recipients in October 2019, on average spent 4 months longer in unemployment, compared to those receiving UI the same month. However, results were insignificant when comparing effects between the inflow of those receiving SA in addition to UI in October 2019 with the inflow of UI recipients the same month. Results for this group were insignificant for both employment outcomes; average earnings and duration to work.
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