STAT 6227, Assignment #2
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STAT 6227, Assignment #2
Nelson-Aalen Estimators, Survival Functions and Bootstrap Procedures
Due Monday, October 24, 2022
Note:
1) It is important to keep your homework, including derivations, explanations and graphs, as kneat and organized as possible, as appearance counts - this will be beneficial for your future professional career. So, if possible, please type your answers.
2) In numerical computations, please provide your computer code, such as SAS or R (Splus) functions, for each numerical result. The code used for this course should be useful for future statistical projects.
Problems:
1. Give a description of the steps for the computation of the Kaplan-Meier estimators of s(t) and the Nelson-Aalen estimators of Λ(t) and their corresponding pointwise bootstrap 95% confidence intervals developed in Efron (1981, JASA).
2. Application to the Survival Functions of the IMRAW-IST data . Compute the following KM estimators for s(t) at t = 1, 3, 5 (in years) and their corresponding pointwise bootstrap 95% confidence intervals based on B = 500 bootstrap samples (you may use the sample sizes of the subgroups as your bootstrap sample sizes):
2.1 the KM estimates and their 95% pointwise bootstrap confidence interval of s(1), s(3) and s(5) for time to death of the IST patients;
2.2 the KM estimates and their 95% pointwise bootstrap confidence interval of s(1), s(3) and s(5) for time to death of the IMRAW patients.
3. Application to the Survival Functions of the IMRAW-IST data . Compute the following KM estimators for s(t) at t = 1, 3, 5 (in years) and their corresponding pointwise Greenwood 95% confidence intervals, and compare these results with the ones in (2.1) and (2.2):
3.1 the KM estimates and their 95% pointwise confidence interval of s(1), s(3) and s(5) for time to death of the IST patients;
3.2 the KM estimates and their 95% pointwise confidence interval of s(1), s(3) and s(5) for time to death of the IMRAW patients.
4. Application to the Hazard Functions of the IMRAW-IST data. Compute the following NA estimators for Λ(t) at t = 1, 3, 5 (in years) and their corresponding pointwise bootstrap 95% confidence intervals based on B = 100 bootstrap samples (you may use the sample sizes of the subgroups as your bootstrap sample sizes):
4.1 the NA estimates and their 95% pointwise bootstrap confidence interval of Λ(1), Λ(3) and Λ(5) for time to death of the IST patients;
4.2 the NA estimates and their 95% pointwise bootstrap confidence interval of Λ(1), Λ(3) and Λ(5) for time to death of the IMRAW patients.
5. Application to the Hazard Functions of the IMRAW-IST data. Compute the following NA estimators for Λ(t) at t = 1, 3, 5 (in years) and their corresponding pointwise Nelson-Aalen 95% confidence intervals, and compare these results with the ones in (4.1) and (4.2):
5.1 the NA estimates and their 95% pointwise confidence interval of Λ(1), Λ(3) and Λ(5) for time to death of the IST patients;
5.2 the NA estimates and their 95% pointwise confidence interval of Λ(1), Λ(3) and Λ(5) for time to death of the IMRAW patients.
2022-10-24