History of Statistics

entry to Survival Analysis 79 7. Topics in cox Regression 7.1 Time-Dependent Covariates It is often the eccentric that the values of some informative variables in a survival abridgment change everyplace time. For example, in Rossi et al.s recidivism information, information on exinmates employment term was collected on a periodical basis. In contrast, other(a) covariates in this info set, such as race and the cookery of ?nancial aid, are time-constant. The Cox-regression model with time-dependent covariates takes the form loge hi(t) = ?(t) + ? 1xi1(t) + ? 2xi2(t) + · · · + ? k xik (t) = ?(t) + xi(t)? ? Of course, not all of the covariates have vary with time: If covariate xj is time-constant, consequently xij (t) = xij .

Sociology 761 Introduction to Survival Analysis > 1 1 1 1 1 1 1 Copyright c 2003 by stern Fox 81 ? For example, the complete initial data record for the ?rst subject is as follows: Rossi[1,] week arrest tailfin age race wexp bollix up paro prio educ emp1 20 1 0 27 1 0 0 1 3 3 0 emp2 emp3 emp4 emp5 emp6 emp7 emp8 emp9 emp10 emp11 0 0 1 1 0 0 0 0 0 0 emp12 emp13 emp14 emp15 emp16 emp17 emp18 emp19 emp20 0 0 0 0 0 0 0 0 0 emp21 emp22 emp23 emp24 emp25 emp26 emp27 emp28 emp29 NA NA NA NA NA NA NA NA NA emp30 emp31 emp32 emp33 emp34 emp35 emp36 emp37 emp38 NA NA NA NA NA NA NA NA NA emp39 emp40 emp41 emp42 emp43 emp44 emp45 emp46 emp47 NA NA NA NA NA NA NA NA NA emp48 emp49 emp50 emp51 emp52 NA NA NA NA NA Sociology 761 Introduction to Survival Analysis 80 Although the inclusion of time-dependent covariates priv y usher in nontrivial data-management issue! s (that is, the construction of a suitable data set can be tricky), the Cox-regression model can considerably handle such covariates. Both the data-management and conceptual treatment of timedependent covariates is facilitated by the so-called counting-process representation of survival data. Copyright...If you command to get a full essay, order it on our website: OrderEssay.net

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