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- Start with 600 cases with an initial fatigue score of 28.5
- Randomly increase the deviation of the scores to simulate some improving and some worsening, cap scores at 33 - the maximum possible fatigue score.
- Watch as the average score magically drops.
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That seems like a fair explanation, though we still have the 'natural boundary' of people with high fatigue scores or low activity scores either refusing to participate or failing to complete. I'm still thinking about ways to incorporate selection bias caused by this effect. Interventions to avoid adverse outcomes (ostensibly for the protection of patients) represent another possible source. The interventions could be more important than the specific treatment.
After a misunderstanding and a blunder, when I did not check something I thought I remembered, I've become more cautious about checking memory. I recall quite a number of adverse events. The protocol requires checking on these, and trying to resolve problems. Naturally they would encourage patients to remain in the study at the same time. We don't know exactly what went on in these cases.anciendaze, do you know if there were interventions during the trial due to adverse events etc? that seems like quite a significant thing to highlight.
After a misunderstanding and a blunder, when I did not check something I thought I remembered, I've become more cautious about checking memory.
I recall quite a number of adverse events. The protocol requires checking on these, and trying to resolve problems. Naturally they would encourage patients to remain in the study at the same time. We don't know exactly what went on in these cases.
There is another problem with words. In medical research literature, an intervention can mean something as dramatic as a heart transplant. The entire therapy applied to a group is technically an intervention in an illness. I'm using the word in a less specific sense. Patients who experienced adverse events had more interactions with research nurses than those without. The number of events reported is high enough to make this as significant as other aspects of the treatment. Since they only intervene to prevent adverse outcomes, this creates a substantial bias.
This is one reason I have trouble remembering what I read in it. Words and numbers keep changing meaning. Contradictions like this cause my mental model of what they are saying to evaporate....So 1 standard deviation changed from 15 to 24 in the course of the study!l
I noticed that in the protocol they say " A score of 70 is about one standard deviation below the mean score (about 85, depending on the study) for the UK adult population.
but in the paper they say " the mean minus 1 SD scores of the UK working age population of 84 (-24) for physical function (score of 60 or more).
So 1 standard deviation changed from 15 to 24 in the course of the study!