Accuracy

Measurements must be accurate bearing in mind:

i) the purpose for which the measurement is made.

e.g. If you are trying to find ' which drug is more potent ' and there is at least a ten-fold difference then a crude measurement is all that is necessary. If the question is 'how much more potent' then a more accurate measurement may be required.

ii) the system on which the measurement is made.

e.g. On a chart recorder calibrated 0-200 mmHg on a 10 cm chart there is no point in trying to measure to 0.01mmHg. The system is simply not discriminating enough.