Ensuring Quality Control
When we carry out repeated tests many times on the same sample of water, it will
rarely happen that we get the same results each time. This is due to the inherent
variability associated with all analytical techniques. Therefore, the result of a water
quality test is only a best-estimate or approximation of the true value of what is being
measured. It is not possible to tell if a test result is exactly right.
Scientific research studies often explain the level of precision including details of the
statistical analysis that was conducted on the results. Statistical analysis of test results
is a complex subject and falls outside the scope of this manual. This section, therefore
presents only a simplified discussion of the most important aspects of quality control