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Stopping Rules

24 Jul, 15 | by Bob Phillips

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 reactions) and some statistical. The latter have with them a set of maths that leads to reasons to discontinue, either for proven benefit or futility.

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There are many ways to truss a duck

21 Jul, 15 | by Bob Phillips

28bd690e07e27d7dfba01e0fc55a63f4And there are lots of ways to do ‘synthesis’ of evidence within a systematic review. We’ve gone on – at length – about meta-analysis and described qualitative synthesis with meta-ethnography, but in a new paper in the Archives we see how a narrative combination of quantitative research studies with a qualitative framework to understand them can allow us to see where the trees lie in the wood [insert alternative forestry based metaphor if preferred].

This group of authors decided to examine the safety netting tools after discharge from the paediatric emergency / urgent care department. more…

StatsMiniBlog: Bonferroni Correction

17 Jul, 15 | by Bob Phillips

20140205-091454.jpgThe 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 of the null hypothesis” (aka – it’s significant! it works!), you need to see the result to be

0.05 / 5 = 0.01  ….  so …

p <0.01 before you can really call it a ‘significant’ result.

– Archi

(It’s a bit harsh. It probably makes you make too many type II errors.)

(You can also apply it to correct confidence intervals. Do five tests, for the ‘real’ 95% confidence interval for each one, you need to calculate the 99% confidence interval.)

Why are you measuring it like that?

14 Jul, 15 | by Bob Phillips

We measure, monitor and assess lots of things in our jobs. We frequently try hard not to think about poorly reproducible some things are – take breathlessness in children as discussed in a recent blog – and the whole literature is methodologically far weaker than that of intervention research. Sometimes we’re really like to assess something, but find it hard to work out exactly how to make that measurement: for example, what should we be measuring when looking at “time to antibiotics” in sepsis – door to ‘needle’ time? proportion less then one hour? first fever to antibiotic duration?

Sometimes it can help to take a completely different idea, to think about what elements might be important.

Say – “home field advantage” in competitive team sports

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StatsMiniBlog: Lead time bias

10 Jul, 15 | by Bob Phillips

http://sci-med-cartoonery.tumblr.com/post/120663951238/whats-so-good-about-early-anyway

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Guest Blog: Addressing Child Poverty

7 Jul, 15 | by Bob Phillips

This Guest Blog, by Caoimhe McKenna, David Taylor-Robinson, Sophie Wickham, Benjamin Barr and Rosie Kyeremateng, addresses the highly political issue of defining child poverty, within the UK context.

We would welcome any and many comments on this blog, and via our usual social media channels! (As always, the libellous and frankly spamming will be blocked, but any other comments will be posted.)

The Government’s plan to repeal the 2010 Child Poverty Act, which committed them to eradicating child poverty in the UK by 2020, and dispense with the current definition of child poverty is highly concerning. This was in the context for a recent report which stated levels of child poverty in the UK were “unacceptably high” and expected to rise (CCs, 2015).

Ian Duncan Smith has indicated that the standard definition of relative child poverty (a household income below 60% of contemporary median) will be replaced with measures of ‘worklessness’, family breakdown, addiction, debt and educational attainment. Details of how this ‘new’ definition of child poverty will be formulated, and what the targets are, have not been outlined. This is concerning because an unvalidated and unclear measure of child poverty may be open to political manipulation.

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StatsMiniBlog: Choosing a test

30 Jun, 15 | by Bob Phillips

StatsMiniBlogThis 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.

blog - how to select a statistical test_1

(Or in a bigger format – click here: blog – how to select a statistical test – with thanks to @drjessmorgan)

Is breathlessness worth reporting at all?

26 Jun, 15 | by Bob Phillips

6za74k736pc03j9fp8h5gialh.500x223x11Again, deliberate bait in the title which I do hope you’re all used to by now …

But the question arose when I started to look at this paper published in the Archives, addressing the question of observer variation in clinical assessment of wheezy kids. Mostly, I think wheeze = mediastinal mass (fast onset -> T-cell lymphoma, slow onset -> Hodgkin’s lymphoma) or wheeze = aspergillus infection, if hot & leukaemic,  but I do recognise that asthma is, occasionally, the correct answer.

But how breathless are wheezers and do different clinicians agree?

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Guest Blog: The trials and tribulations of answering clinical questions

23 Jun, 15 | by Bob Phillips

 For a recent evidence based paediatrics assignment we had to answer and present a clinical question. I’m sure you are well acquainted with the process; construct your question in standard PICO format, search your secondary and primary sources, critically appraise the evidence and draw your conclusions.

Having noted a trend towards starting lamotrigine rather than valproate in adolescent girls, because of the concerns of teratogenicity, and wondering if this is at the expense of good seizure control, my question was:“In adolescent girls with newly diagnosed generalised epilepsy (population) is lamotrigine (intervention) as effective as sodium valproate (comparison) at achieving seizure control (outcome)?”

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Basics: Another way to look at it all

19 Jun, 15 | by Bob Phillips

While the theory of different styles of learning (kinetic, verbal, visual etc etc ) may be thoroughly garbage it’s pretty much true that folk often prefer one way of getting their learning. Some like listening – catch our podcasts for that – others doing – so we have #ADC_JC – and many readers of this blog will like, well, reading.

Anyone particularly value pictures?

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