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Tim Morris@timpmorris.bsky.social |
461 followers 175 following 587 posts
Principal research fellow in statistical methods. Work on simulation studies, missing data, estimands, covariate adjustment…
He/him
tpmorris.substack.com/
profiles.ucl.ac.uk/2059
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Harlan
@harlanhappydog.bsky.social
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“Evidently, there has been a lack of clarity about the precise definition of these terms, and the relationships between them. We provide a set of recommended definitions in Table 1.”
onlinelibrary.wiley.com/doi/full/10....
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Tim Morris
@timpmorris.bsky.social
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Perfect, thanks Harlan!
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Tim Morris
@timpmorris.bsky.social
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Agree. Also, though he says a lot of good stuff that gets you thinking, it’s often not enough to know quite what his point is!
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Jess Rohmann
@jlrohmann.bsky.social
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Biomedical science folks: Curious to learn more about peer-review and the scientific publishing landscape as a whole? Want hands-on, group reviewing experience with an editor-mentor? Apply now for our next run of Peerspectives, fully online, starting this fall: forms.gle/assQnYNgpaav... (due Aug 1)
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Tim Morris
@timpmorris.bsky.social
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Cool!
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Tim Morris
@timpmorris.bsky.social
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😂
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Tim Morris
@timpmorris.bsky.social
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Makes me wonder how the structure we use for estimands in clinical trials would go down in psychology!
#stats
www.bmj.com/content/384/...
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Tim Morris
@timpmorris.bsky.social
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Thanks for posting!
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Matt Cooper
@nzcoops.bsky.social
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A great reminder of what "sensitivity analysis" is (or should be), before just diving in.
Nomenclature in stat can be very risible (WOTD) but we have to try and stay on top of it!
bmcmedresmethodol.biomedcentral.com/articles/10.... @timpmorris.bsky.social
#StatsSky #Stats #RStats
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Tim Morris
@timpmorris.bsky.social
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Slightly scared someone will go 'that's fine, it counts as a Gibbs sampler!'
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Tim Morris
@timpmorris.bsky.social
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New blog post: MICE is not a Gibbs sampler
open.substack.com/pub/tpmorris...
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Julia M. Rohrer
@dingdingpeng.the100.ci
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This semester I taught matching for the very first time, so I had to look up a lot of stuff. Whenever I found an answer and thought “perfect, that’s exactly what I was looking for”, it turned out to be written by @noahgreifer.bsky.social 🙏
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Tim Morris
@timpmorris.bsky.social
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Observed effect sizes from your study is what we’re talking about
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Tim Morris
@timpmorris.bsky.social
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You’re right. Post hoc power is a nonsense concept. The notion of power is useful for planning but not once the results are in.
I like this paper by Andrew Althouse.
www.journalofsurgicalresearch.com/article/S002...
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Tim Morris
@timpmorris.bsky.social
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Ronaldo might start crying soon folks
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Tim Morris
@timpmorris.bsky.social
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Unhelpful, sorry. Do you know where those spikes are from? Is it a visualisation artefact, e.g. using 4 bins for every 5 possible values of sensor stress, so that every fourth bin includes two integer values instead of one and that makes it spike?
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Tim Morris
@timpmorris.bsky.social
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Tim Morris
@timpmorris.bsky.social
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Enjoying that NaN at the bottom right
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Tim Morris
@timpmorris.bsky.social
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I don’t know how to break this to you but… Max Parmar is about as frequentist as they come
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Tim Morris
@timpmorris.bsky.social
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Thinking about this more, upstrap approach seems to achieve the same thing as simply analysing the interim data but replacing n_interim with n_target when calculating in the SE.
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Tim Morris
@timpmorris.bsky.social
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I think you aggregate over the whole lot right? Because power will be a frequency over all upstrap samples. Have I misunderstood?
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Tim Morris
@timpmorris.bsky.social
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Is doing this at interim analysis somehow better because we get to make the decision about whether we want to see the bigger trial? Or is ignoring inherent noisiness of interim estimates still problematic? I really haven't thought much about it so these are actual questions. 4/
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Tim Morris
@timpmorris.bsky.social
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We tut when people interpret their studies as 'result wasn't significant but with a bigger trial it would have been' because a bigger trial would not just tell us the same thing. 3/
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Tim Morris
@timpmorris.bsky.social
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This seems close in spirit to plugging in interim estimates to your original power calculation and finding out power given your originally-planned sample size. Upstrap adds a bit of sophistication by allowing for model misspecification. 2/
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Tim Morris
@timpmorris.bsky.social
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Just skimming over this paper on 'upstrapping' for interim analyses of trials. Idea involves repeated simulation where you resample-with-replacement n (full trial size) from <n (interim sample size) and look at result.
Not convinced.
1/
trialsjournal.biomedcentral.com/articles/10....
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Tim Morris
@timpmorris.bsky.social
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Nice. I suggest grappling publicly with the notion that what you do may not matter. That one got some good engagement.
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Tim Morris
@timpmorris.bsky.social
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Erupted only has one r doesn’t it oh dear oh dear
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Tim Morris
@timpmorris.bsky.social
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Oh no, has this errupted somewhere again?
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Tim Morris
@timpmorris.bsky.social
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Haven’t heard from them in a while… or perhaps ever. Are they active?
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Tim Morris
@timpmorris.bsky.social
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Reminder of our (unconstructive) paper on the marginality principle. tldr: the scale on which you happened to measure a variable does not justify how you include it in a regression model.
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Tim Morris
@timpmorris.bsky.social
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If you want to be a marginality extremist you have to not understand that it’s just a syntactic distinction, Will. I don’t make the rules. You’re a true marginality believer if you disagree with the BPM example and think that modelling beats and minutes separately is better.
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Tim Morris
@timpmorris.bsky.social
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Oh no, marginality extremists! 😜
onlinelibrary.wiley.com/doi/10.1002/...
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Tim Morris
@timpmorris.bsky.social
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Exactly. The way to make bluesky flop is to do a mastodon and make the whole thing about twitter. The way to make it work is to make sure it’s a vaiable alternative when twitter implodes.
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Darren Dahly
@statsepi.bsky.social
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Tip: We aren't comparing the effect of the treatment (tx) to the effect of placebo. We are *defining* the effect as the *difference* in outcome between those allocated to standard of care (SoC) + tx to those allocated to SoC + placebo, where placebo is used for blinding.
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Tim Morris
@timpmorris.bsky.social
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Putting an s on the end of supermarket names is a cockney hallmark. Your kids will be in awe once you tell them that nugget.
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Tim Morris
@timpmorris.bsky.social
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You’re in! This is shaping up the be a helluva night
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Tim Morris
@timpmorris.bsky.social
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Indeed. At this point what’s one more!
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Tim Morris
@timpmorris.bsky.social
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In network meta-analysis, do ‘transitivity’ and ‘consistency’ have different meanings? I’m reading something on transitivity and it seems to be the same concept. Am I missing something?
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Tim Morris
@timpmorris.bsky.social
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I still think it would be amazing to go out drinking with whoever picks out stuff for the middle aisles in Lidl and Aldi
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Tim Morris
@timpmorris.bsky.social
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My unit director Max Parmar is kicking off LSHTM’s annual ‘Perspectives on Statistics in Medicine’ lecture
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Tim Morris
@timpmorris.bsky.social
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Oh me pick me I know this one! There’s a constant union betwixt the cause – UNIMPRESSIVE ATE DESPITE STRONGLY HELD HUNCHES – and effect – I THINK I’LL FIND IT’S A NOT MORE COMPLICATED THAN ATE CAPTURES
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Tim Morris
@timpmorris.bsky.social
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Another banger Julia! Interesting point on 'starts from the opposite notion that causal effects are the same for everyone'. Seems similar in experimental design literature. Often 'assuming this model [where all individual causal effects are identical], then the optimal design…'
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Tim Morris
@timpmorris.bsky.social
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Thanks Anne, that makes sense. Superb paper title, bravo! I'll have a read.
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Tim Morris
@timpmorris.bsky.social
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Curious about 'their connection to substantive hypotheses is usually ill-defined'. Do you mean this empirically – researchers do tests that don't target what they think – or another way?
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Tim Morris
@timpmorris.bsky.social
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Once heard someone describe multiple outputation as defunct-when-born but would have been life-changing had it been invented 40 years earlier when computers were less powerful.
onlinelibrary.wiley.com/doi/abs/10.1...
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Tim Morris
@timpmorris.bsky.social
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‘Top-2% cited, yet not suspiciously prolific if we define the latter as more prolific than me’
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Tim Morris
@timpmorris.bsky.social
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It’s like going back in time 3–4 years!
Wonderful little JPAI special about ‘top-2% cited scientists’ under ‘Contributors and sources’ 🙃
www.sciencedirect.com/science/arti...
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Tim Morris
@timpmorris.bsky.social
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I was selfishly disappointed by child-free day. After initially being filled with wonder, I realised I’d completely misunderstood and it’s for the people who are also child-free on the other 364 days.
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Tim Morris
@timpmorris.bsky.social
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Perfect! The date for Estimands Day seems important right? Ideally when there are often conferences on… and a bit before Assumptions Day?
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Tim Morris
@timpmorris.bsky.social
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Great! Can we just name the date or is there something official you have to do to get the ‘___ day’ designation?
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