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StatsMiniBlog: Subgroup or sensitivity analyses?
Perhaps becoming a little obscure, but there are some folk in the world who become concerned about undertaking analysis in systematic reviews. Some of these are described as “subgroup” analysis,...
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StatsMiniBlog: Odds and Probabilities
There’s something that is frequently wittered about but the odds are you’ve never really been bothered enough to care if there’s a difference between ‘probability’ and ‘odds’ (like relative risk and...
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Sensitivity and specificity
Sensitivity and specificity are those sorts of things that can really get knickers twisted up something rotten. They sound like something you should be able to understand, they get used as if you...
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Positive about predictions
In a previous post I muttered about how unhelpful sensitivity and specificity are to practicing clinicians, and how what we really want to know are the predictive values of a test. Remembering the...
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Gambling, alcohol and division.
No, not an average afternoon at the Houses of Parliament, but another in our diagnostics series. Moving yourself from looking at the predictive values of the tests as evaluated, to taking this...
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StatsMiniBlog: Z scores.
A recent journal club article, the exact nature of which is irrelevant, triggered a coffee-room discussion on the subject of z scores, which although often understood in relation to Bone Mineral...
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StatsMiniBlog: ROC plots
A (while ago) we published an explanatory page about ROC plots in the Education and Practice journal. There are a few great reasons why we should replicate it here: 1. So people can read it more easily...
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StatsMiniBlog: Incidence and Prevalence
There are two relatively simple terms that get splattered about and are sometimes confused and can cause all sorts of difficulties. Incidence – the number of people who develop a condition in a...
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StatsMiniBlog: Spot on, time and again.
“Spot on!” is a rather anachronistic and very Anglophile phrase, redolent of croquet lawns, tweeds and well designed woven straw hats. It’s no wonder we tend to use – if we are being technical – the...
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Guest Blog: Sampling bias and randomisation
The blog series is expanding! No doubt soley inspired by now running the magnificent @ADC_JC, @davidking83 has taken up the challenge of exploring a critical appraisal nugget/thorn in response to an...
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StatsMiniBlog: Will Rogers Phenomenon
The American humorist, Will Rogers, was reported to have said (of the migration of folk from Oklahoma to California): When the Okies left Oklahoma and moved to California, they raised the average...
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StatsMiniBlog: Surrogate, proxy or process?
When we look at treatments for children’s ill health, we tend to be stuck in a pleasant dilemma. We normally want to use treatments to stop kids dying, and to make them better quicker – but it’s...
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StatsMiniBlog: Cronbach’s alpha
When you’re next handing out your questionnaire in clinic, or on the wards, or sit out in the library assessing the results of a recent clinical study, will you be asking about the quality of the...
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StatsMiniBlog: Causal Analysis
A while back, we looked at propensity scores as a way of adjusting / controlling for confounders in non-randomised designs. Another approach is the hypothesis-driven estimation of an ‘instrumental...
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StatsMiniBlog: Complex vs. Complicated
These two words, though often used synonymously are different – do you know how? It’s actually not that difficult. Complicated = made of lots of parts, but “logical and rational” — like a car engine,...
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StatsMiniBlog: Recursive partitioning
If you want to know who does, and who does not, need a bone marrow biopsy to detect malignant infiltration if the patient has rhabdomyosarcoma, you might want to start by taking a very large cohort of...
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StatsMiniBlog: I-squared
No, not -1, the self-multiplication of that fancy imaginary number that helps aircraft designers make wings work properly, but a (semi) quantitative assessment of how much heterogeneity there is in a...
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StatsMiniBlog: Cluster analysis
Lumps and groups and clumps and factors … all sorts of ways of describing how Things Can Be Similar. Cluster analysis is a statistical term that refers to an approach – not a particular method – that...
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StatsMiniBlog: Choosing a test
This is a very, very simple approach to picking a method of analysis for a research study (that’s looking at one comparison, and with lots of caveats – this is VERY simple) … but as a start, you may as...
View ArticleMiniStatsBlog: Lead time bias
http://sci-med-cartoonery.tumblr.com/post/120663951238/whats-so-good-about-early-anyway This is a cracking cartoon that highlights everything that’s misleading about lead time bias. And will also lead...
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