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http://bahrain.cochrane.org http://www.rt.ae. Cochrane Collaboration and Systematic Review Workshop, 20-21 February 2007, Dubai - UAE. The Bahrain Branch of the UK Cochrane Centre In Collaboration with Reyada Training & Management Consultancy, Dubai-UAE. W07.
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http://bahrain.cochrane.org http://www.rt.ae Cochrane Collaboration and Systematic Review Workshop, 20-21 February 2007, Dubai - UAE The Bahrain Branch of the UK Cochrane Centre In Collaboration with Reyada Training & Management Consultancy, Dubai-UAE W07 Dr. Zbys Fedorowicz, Dr. Dunia Al Hashimi, Dr. Ahmed Al Asfoor
Random allocation • A method that uses the play of chance to assign participants to comparison groups in a trial • e.g. by using a random numbers table or a computer-generated random sequence. • Random allocation implies that each individual or unit being entered into a trial has the same chance of receiving each of the possible interventions. • It also implies that the probability that an individual will receive a particular intervention is independent of the probability that any other individual will receive the same intervention.
Quasi-random allocation • Methods of allocating people to a trial that are not random, but were intended to produce similar groups when used to allocate participants. • Quasi-random methods include allocation by: • Date of birth, • Day of the week or month of the year, • Medical record number, • Every alternate person. • In practice, these methods of allocation are relatively easy to manipulate, introducing selection bias.
Randomisation • The process of randomly allocating participants into one of the arms of a controlled trial. • There are two components to randomisation: • the generation of a random sequence, • its implementation, • ideally in a way so that those entering participants into a study are not aware of the sequence (concealment of allocation).
Randomised controlled trial (RCT) • Best form of healthcare evidence, or the “gold standard” for evidence about an intervention. • lack of randomisation can give a 40 % over or underestimate of treatment effect synthesis of those trials statistical and clinical heterogeneity.
Hierarchy of Evidence Meta-analysis of RCTs systematic review of RCTs Individual RCT Observational studies patient-important outcomes Basic research test tube, animal, human physiology Clinical experience