Độc giả có thể tìm thấy các mã hữu ích. Phần 11,8 giới thiệu hai mô hình khác. Trong phần 11,9 chúng tôi thảo luận về các phương pháp lựa chọn mô hình và sự tốt lành của các xét nghiệm phù KIỂM TRA thông tin dữ liệu liên quan đến yếu tố tiên lượng có thể có thể thu được từ nghiên cứu lâm sàng được | PRELIMINARY EXAMINATION OF DATA 257 can be used to fit the models are given at the end of the examples. Readers may find these codes helpful. Section introduces two other models. In Section we discuss the model selection methods and goodness of fit tests. PRELIMINARY EXAMINATION OF DATA Information concerning possible prognostic factors can be obtained either from clinical studies designed mainly to identify them sometimes called prognostic studies or from ongoing clinical trials that compare treatments as a subsidiary aspect. The dependent variable also called the response variable or the outcome of prediction may be dichotomous polychotomous or continuous. Examples of dichotomous dependent variables are response or nonresponse life or death and presence or absence of a given disease. Polychotomous dependent variables include different grades of symptoms . no evidence of disease minor symptom major symptom and scores of psychiatric reactions . feeling well tolerable depressed or very depressed . Continuous dependent variables may be length of survival from start of treatment or length of remission both measured on a numerical scale by a continuous range of values. Of these dependent variables response to a given treatment yes or no development of a specific disease yes or no length of remission and length of survival are particularly common in practice. In this chapter we focus our attention on continuous dependent variables such as survival time and remission duration. Dichotomous and multiple-response dependent variables are discussed in Chapter 14. A prognostic variable or independent variable or factor may be either numerical or nonnumerical. Numerical prognostic variables may be discrete such as the number of previous strokes or number of lymph node metastases or continuous such as age or blood pressure. Continuous variables can be made discrete by grouping patients into subcategories . four age subgroups 20 20-39 40-59 and 60 . .
