As its summer time & thoughts of exciting summer camps expanding skills, or time spent catching up with missed opportunities, or indeed just beer & strawberries, are filling our lives it seems appropriate to go entirely left field and explore confidence intervals. Confidence intervals describe – in terms of interpretation – the range of values […]
Category: stats
StatsMiniBlog: Calibration vs Discrimination
There are a variety of clinical prediction rules in the world. If you’ve seen one – they always used to have a nomogram attached – it would take the answers to a few questions and come up with a ‘probability of bad thing happening’. As we’ve mentioned previously, there’s an issue with deriving models and assuming they will work […]
Stopping Rules
If you were cycling or driving, you’d probably know what the stopping rules were. Traffic not moving, big red sign, large goose with malevolent glare (Lincolnshire speciality). What if you’re doing a clinical trial? There are a variety of things what have been described, some of them are qualitative (SUSAR – sudden, unexpected, serious adverse […]
StatsMiniBlog: Bonferroni Correction
The Bonferroni Correction is the simplest, the most understandable, and the most extreme way of correcting for multiple statistical tests. You take your ‘significance’ level and divide by the number of tests you are doing. So if you have set ‘significance’ at 0.05, and do 5 different statistical tests, to be actually sure that your “rejection […]
StatsMiniBlog: Lead time bias
http://sci-med-cartoonery.tumblr.com/post/120663951238/whats-so-good-about-early-anyway […]
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 well go with this picture. (Or in a bigger format – click here: blog – […]
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 seeks to work out how to group items together so those in the same group are maximally similar […]
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 meta-analysis: I² You’ll recall that the idea of heterogeneity (mixed-up-ness) comes in both statistical and clinical flavours. This measure – I² – assesses the statistical […]
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 patients who had RMS and had a load of tests, including marrows. Then construct a decision tree that settles […]
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, 10001 piece jigsaw of the Gobi desert, or (dare I say it) a heart Complex = constructed with pieces with […]