I have an st-dataset of cancer patients and 50 sex- and age-matched population controls per case. They are from four calender time periods (1985-89, 1990-94, 1995-99, 2000-03). I want to examine whether the prognosis for cancer patients is getting better, taking into account that the prognosis for the general population may vary. For each period, I calculate the relative survival as the 5-year survival probability of cancer patients divided by the 5-year survival probability of controls. The survival probabilities are obtained with sts list, by(case) at(5).
Then I calculate the relative relative survivals using 1985-89 as reference, i.e. I divide the relative survival for 1990-94 (and 1995-99 and 2000-03) with the relative survival for 1985-89.
My question is this: How do I calculate a 95% confidence interval for the relative relative survivals?
Thank you in advance for any help.
Peter Jepsen.
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