Page 19 - Quality control of pharmaceuticals (07-PA 704)

An important aspect of the quality control is the detection of both
random and systematic errors. This can be done by critically
looking at the performance of the analysis as a whole and also of the
instruments and operators involved in the job.

1. Random Errors
Random errors are ones that are easier to deal with because they cause the
measurements to fluctuate around the true value. If we are trying to
measure some parameter X, greater random errors cause a greater
dispersion of values, but the mean of X still represents the true value
for that instrument.

2. Systematic Errors
This error is often called a bias in the measurement.
Example: Reading the volume of liquid in a buret by looking at the

meniscus. A student may make an error in reading the volume by
looking at the liquid level near the edge of the glass. Thus this student
will always be off by a certain amount for every reading he makes.
This is a systematic error.
Instruments often have both systematic and random errors.