[Stats] the placebo arm lost weight too. always ask by how much.
the placebo arm lost weight too. always ask by how much — a position I have arrived at slowly and would like tested.
Why comparing across trials almost never works, with the specific failure modes.
Different populations: an obesity programme and a diabetes programme enrol different people with different baseline characteristics. Different endpoints: body weight change, glycaemic control and cardiovascular events are not convertible. Different durations: 68 weeks and 72 weeks are not the same, and the curves have not flattened by either.
Different analysis populations: one paper reports intention-to-treat, another emphasises completers. Different support: some trial designs include structured lifestyle contact that no member of this board receives.
Stack those and the "X beats Y" tables that circulate here are comparing five things at once and attributing the difference to the molecule.
A confidence interval is the range of effects compatible with the data. Two trials with overlapping intervals have not disagreed, whatever their point estimates look like next to each other.
Intention-to-treat analyses everybody randomised regardless of what they did afterwards. Completer analyses only those who finished. The second is systematically more flattering and both are legitimate if labelled.
Not medical advice, obviously, and nothing here is approved for human use. One person with a spreadsheet.
best — the order this archive was captured in
Cardiovascular outcome trials are powered for events, not for weight, and are typically run in a different population with different inclusion criteria. Reading a weight number out of one is reading a secondary endpoint.
Relative risk reduction without the baseline rate is uninterpretable. A large relative reduction on a small absolute risk is a small absolute benefit.
That is the 68-week readout, not the 72-week one. Different trial, different duration.
This. Intention-to-treat versus completer analysis routinely moves the headline by several points.
Quoted a figure here confidently, got asked whether it was ITT, went and checked, and it was not. Learned something.
What did the confidence interval look like?
Compared myself to a trial mean for about six months before realising the trial arm had dietitian contact every fortnight.