| An independent statistician prepared the randomisation envelopes using a computer based random number generator. |
| Despite these limitations, descriptive studies, interpreted with suitable caution, can offer some useful insight to complement the data from studies using randomisation. |
| Patients were randomly allocated into the CPAP group or the control group using a computer-generated randomisation list. |
| We also recruited a large number of clusters and performed statistical analyses taking cluster randomisation into account. |
| However, use of cluster randomisation rapidly leads to a doubling of the sample size. |
| We measured outcomes at two months and four months after randomisation by mailed questionnaires. |
