| An independent statistician prepared the randomisation envelopes using a computer based random number generator. |
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| The actual randomisation was provided to the statistician only at the final analysis. |
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| For randomisation, patients were stratified according to hospital and treatment intent. |
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| After randomisation, all children were tested for refractive error with cycloplegic drops to eliminate artefact due to accommodation. |
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| We also recruited a large number of clusters and performed statistical analyses taking cluster randomisation into account. |
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| However, use of cluster randomisation rapidly leads to a doubling of the sample size. |
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| We measured outcomes at two months and four months after randomisation by mailed questionnaires. |
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| Despite these limitations, descriptive studies, interpreted with suitable caution, can offer some useful insight to complement the data from studies using randomisation. |
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| All baseline data and measurements were recorded before randomisation. |
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| It is possible to conceal the randomisation in every randomised trial. |
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| Patients were randomly allocated into the CPAP group or the control group using a computer-generated randomisation list. |
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| Sulfonylureas and glinides were discontinued at randomisation. |
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