Seeking expertise on the hazard ratio (HR) analysis. When I analyze all the 3 groups of data together, I get the Exp(B) as shown in second figure. However, if only the first and third groups are analyzed , Exp(B) become different as shown in the third figure. Why are they different? and which one is correct?
Assuming you dummy-coded the groups (0 and 1), what is the reference group in either of these analyses? This should explain the discrepancy. Also, standard errors, test statistics, and p values may differ between analyses with 2 vs. 3 groups.
Hi Christian Geiser, Many thanks for your answer. The first 4 rows are are reference group. The middle 4 rows and last 4 rows are two treatment groups. The first 4 rows was used as reference category.
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