I have a randomized controlled trial with three groups and three time measurements (pre, post, follow-up). I noticed that from pre to post, and then from post to follow-up, the attrition rates seem different by group. A reviewer asks whether the differential attrition is statistically significant.
Here is example data:
data <- data.frame( group = c("Control", "Treatment1", "Treatment2"), pre = c(150, 150, 150), post = c(150, 100, 80), follow = c(120, 90, 70) ) data #> group pre post follow #> 1 Control 150 150 120 #> 2 Treatment1 150 100 90 #> 3 Treatment2 150 80 70
Created on 2023-11-10 with reprex v2.0.2
Can I really do a statistical test with just 6 values at a time? I was thinking of two tests: one for attrition from pre to post, and another test for attrition from post to follow-up. If so, what test?
I read from this source and this source that there are two primary tests used in this context: (a) differential attrition rate tests and (b) selective attrition tests. Are these tests appropriate for my data? And how can I conduct these tests in R?