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Dictionary of Evidence-based Medicine.pdf

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<strong>Dictionary</strong> <strong>of</strong> <strong>Evidence</strong>-<strong>based</strong> <strong>Medicine</strong> 25<br />

is to construct a summary statistic for each cluster (school) and then<br />

analyse these summary values (Bland JM, Kerry SM (1997) Statistics notes.<br />

Trials randomised in clusters. BMJ. 315: 600. Kerry SM, Bland JM (1997)<br />

Analysis <strong>of</strong> a trial randomised in clusters. BMJ. 316: 54).<br />

Cluster sampling<br />

In cluster sampling members <strong>of</strong> the population to be sampled are first<br />

arranged into groups or clusters. The clusters are sampled and those<br />

selected are subsampled. Such cluster sampling is <strong>of</strong>ten multistaged. A<br />

recent study is illustrative. The investigators wanted to draw a sample <strong>of</strong><br />

12-17-year-olds from the Community Health Index (a listing <strong>of</strong> names and<br />

addresses <strong>of</strong> people registered with general practitioners within their<br />

health board). The sampling frame consisted <strong>of</strong> all postcode sectors. Thirty<br />

sectors were sampled. These sectors were stratified according to district<br />

and Carstairs score (a measure <strong>of</strong> affluence or deprivation within an area)<br />

and a sample <strong>of</strong> 40 people aged 12-17 years inclusive was drawn from each<br />

using a random procedure stratified by age and sex (Hughes K, McKintosh<br />

AM, Hastings G et al. (1997) Young people, alcohol and designer drinks:<br />

quantitative and qualitative study. BMJ. 314: 44-8).<br />

CMA (see Cost minimization analysis)<br />

Cochrane, Archie (1909-88)<br />

A visionary Scottish physician whose criticism <strong>of</strong> the medical pr<strong>of</strong>ession<br />

for not organizing 'a critical summary, by specialty or subspecialty, adapted<br />

periodically, <strong>of</strong> all relevant randomized trials' to guide practice acted as a<br />

catalyst for the establishment <strong>of</strong> the Cochrane Collaboration (see Cochrane<br />

A, Blythe M (1989) One man's medicine. An autobiography <strong>of</strong> Pr<strong>of</strong>essor Archie<br />

Cochrane. BMA, London).<br />

Cochrane Collaboration<br />

A collaborative network focusing on undertaking and making accessible<br />

systematic up-to-date reviews <strong>of</strong> randomized controlled trials <strong>of</strong> health<br />

care. The collaboration is named after Archie Cochrane, a Scottish physician.<br />

Initial funding was provided by the UK Department <strong>of</strong> Health to set<br />

up the UK Cochrane Centre but the collaboration is now international with<br />

a number <strong>of</strong> national and regional centres co-ordinating the work <strong>of</strong><br />

collaborative review groups and networks within their regions. The main

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