Some laboratory procedures inevitably lead to variation in reported results even though the
procedures are correctly performed.
This may lead to confusion with the natural variation due
to “sampling error”.
Hence, a result that is reported with an estimated 95% confidence
interval may be misunderstood.
While it may be assumed that the confidence interval applies
to the bacterial density of the water source, it could refer to the confidence interval resulting
from the laboratory procedures, which, as already stated in section
5.1, are generally much
smaller.
Errors due to faulty sampling or laboratory procedures and equipment, etc (i.e. uncertainty of
measurement) are not fully discussed in this booklet.
