Over the past several decades, the incidence of thyroid cancer in the United States has increased substantially surmounting to higher levels of concern for physicians around the nation. This concern led to a research investigation surrounding the increased risk thyroid cancer patients may face by delaying their surgeries. OBJECTIVE: We aim to evaluate the impact of a delay in surgical intervention on survival in patients with a diagnosis of papillary thyroid cancer. METHODS: This is an observational retrospective study focusing on disease specific survival using SEER-Medicare data as well as data from the National Cancer Database to analyze whether a delay in surgical intervention leads to a decrease in mortality in patients with papillary thyroid cancer. This study focuses on specific thyroid cancer association beyond that of another research paper that found delaying time to surgery does decrease overall survival as discovered by Dr. Scott Fligor in 2021. For the purposes of this study, data was accessed between the years 1999-2018. A survival analysis was performed using the Cox- hazard ratio as well as Kaplan-Meier curves. RESULTS: Preliminary results detail the fact that delaying surgeries past 180 days for patients led to decreased survival over a course of 5, 10, and 15 years as was determined by the use of Kaplan Meyer curves and the Cox hazard ratio. A positive coefficient for a Cox hazard ratio indicates a worse prognosis whereas a negative coefficient indicates the opposite. The results of this study show that increasing time to surgery increases risk of mortality for patients as the hazard ratios suggest for this research. The hazard ratio for 90 – 180 days delay for patients versus patients who underwent surgery within 0 – 90 days was 1.18 (95% confidence internal, 0.96 – 1.45). This hazard ratio is lower than that of the group that underwent surgery after 180+ days whose hazard ratio was 1.21 (95% confidence internal, 0.89 – 1.66). Since the hazard ratio for patients who delayed surgery after 180+ days is higher than the 0 – 90 days as well as the 90 – 180 days, this indicates a worse prognosis over time for patients with increased delays. CONCLUSION: Delaying surgery for thyroid cancer patients deceases their overall survival over a period of 5, 10, and 15 years. Elective or lower risk surgeries over the past 3 years have been delayed due to the Covid-19 pandemic, and thus this data was excluded for the purposes of this study. Further research should be done on the effects the pandemic had on the overall survival for patients who had to delay their surgeries due to the pandemic.

published_or_final_version / abstract / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Statistics / Doctoral / Doctor of Philosophy

published_or_final_version / Statistics and Actuarial Science / Master / Master of Philosophy

Gays and lesbians have long struggled for their rights as citizens, yet only recently has their struggle been truly politicized in a way that fosters mobilization. When and why social movements coalesce despite the many obstacles to collective action are fundamental questions in comparative politics. While examining social movements is worthwhile, it is important to examine not only when and why a social movement forms, but also when and why a social movement is successful. This dissertation tackles the latter of these objectives, focusing on when and why social movements have success in terms of their duration from the time of their formation until their desired policy output is produced.

No description available.

This thesis investigates the use of newly-developed survival analysis tools for credit scoring. Credit scoring techniques are currently used by financial institutions to estimate the probability of a customer defaulting on a loan by a predetermined time in the future. While a number of classification techniques are currently used, banks are now becoming more concerned with estimating the lifetime of the loan rather than just the probability of default. Difficulties arise when using standard statistical techniques due to the presence of censoring in the data. Survival analysis, originating from medical and engineering fields, is an area of statistics that typically deals with censored lifetime data. The theoretical developments in this thesis revolve around linear regression for censored data, in particular the Buckley-James method. The Buckley-James method is analogous to linear regression and gives estimates of the mean expected lifetime given a set of explanato ry variables. The first development is a measure of fit for censored regression, similar to the classical r-squared of linear regression. Next, the variable-reduction technique of stepwise selection is extended to the Buckley-James method. For the last development, the Buckley-James algorithm is altered to incorporate non-linear regression methods such as neural networks and Multivariate Adaptive Regression Splines (MARS). MARS shows promise in terms of predictive power and interpretability in both simulation and empirical studies. The practical section of the thesis involves using the new techniques to predict the time to default and time to repayment of unsecured personal loans from a database obtained from a major Australian bank. The analyses are unique, being the first published work on applying Buckley-James and related methods to a large-scale financial database.

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Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 110-114).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 81-86).