Читать книгу Randomised Clinical Trials - David Machin - Страница 27

Measurements made on human subjects rarely give exactly the same results from one occasion to the next. Even in adults, our height varies a little during the course of the day. If one measures the blood sugar levels of an individual on one particular day and then again the following day, under exactly the same conditions, greater variation in this than that of height would be expected. Hence were such an individual to be assessed and then receive an intervention (perhaps to lower blood sugar levels) any lowering recorded at the next assessment cannot necessarily be ascribed to the intervention itself. The levels of inherent variability may be very high so that, perhaps in the circumstances where a subject has an illness, the oscillations in these may disguise, at least in the early stages of treatment, the beneficial effect of the treatment given to improve the condition.