Hi all,

I am trying to run Weibull PH model  in R.

Assume in the data set  I  have x1  a continuous variable and x2 a
categorical  variable with two classes (0= sick and 1= healthy).  I fit the
model in the following way.

Test=survreg(Surv(time,cens)~ x1+x2,dist="weibull")

My questions are

1. Is it Weibull PH model or Weibull AFT model?
Call:
survreg(formula = Surv(time, delta) ~ x1 + x2, data = nn,
    dist = "weibull")
                    Value         Std. Error      z          p
(Intercept)   5.652155    3.54e-02        159.8   0.00e+00
x1                0.492592    1.92e-02        25.7   3.65e-145
x2               -0.000212    5.64e-06      -37.6    0.00e+00
Log(scale)  -0.269219     1.57e-02      -17.1   1.24e-65
Scale= 0.764

2. I am interested in comparing the two classes of x2 (short, medium and
long) using the Weibull PH model. So I used factor(x2) in the model

Call:
survreg(formula = Surv(time, delta) ~ factor(x1) + x2, data = nn
    dist = "weibull")
                    Value         Std. Error     z         p
(Intercept)      6.192157   2.35e-02  263.5   0.00e+00
factor(x1)2     0.324327   3.14e-02   10.3    4.51e-25
factor(x1)3     1.038423   4.13e-02   25.1    2.07e-139
x2                 -0.000211   5.64e-06  -37.4    7.89e-306
Log(scale)    -0.267627   1.57e-02   -17.0    5.63e-65

Scale= 0.765

How do I interpret those results?

Is there a relationship between Webull PH and AFT Model?




Thanks

Val

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