Nếu tất cả các thông tin bạn cần thiết có thể được thu thập tại một trang web duy nhất, kết quả sẽ được giảm ngay lập tức biến thể bệnh nhân để bệnh nhân với một giảm đi kèm trong kích thước mẫu cần thiết. | PRACTICAL STEPS YOU CAN TAKE TO REDUCE LOSSES Target recruiting efforts at those both eligible and likely to participate See Chapter 9 . Review and if possible loosen eligibility requirements. Select appropriate partici- pants . ones most likely to remain in compliance. Establish measures to increase compliance see Chapter 5 . yet-to-occur losses before settling on a final figure for the size of the initial sample. NUMBER OF TREATMENT SITES If all the information you needed could be collected at a single site the result would be an immediate reduction in patient-to-patient variation with an accompanying decrease in the necessary sample size. But that s not going to happen particularly if the disease condition you hope to treat is a relatively rare one. Even if it could happen you might want to use multiple sites if you felt it would reduce the total time required to complete the trials. Either way you need to have some advance notion of the number of patients you might hope to treat at each site which means you have to have some notion of the prevalence of the disease condition. If you come up with less than six patients per site then you will need to increase the duration of your study in order to enroll sufficient eligible patients see also Chapter 9 . Once you have this number in hand you can divide the sample size by it to determine the number of physicians you will need to recruit. ALTERNATE DESIGNS KISS is the operative phrase in the design of the large-scale long-term randomized controlled clinical trials that are the chief concern of this volume. We advise you to resist all attempts to measure redundant variables But surely as long as the patient is in my office you won t mind if I perform one or two tests of my own or complicate the design. On the other hand short-term clinical trials of more limited scope whose objective is to determine the maximum tolerable dose or to establish efficacy can often benefit from the use of more complex experimental .
