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o p e r a t i n g t h e a n a l y z e r
Random Errors
An isolated result which falls outside the +/- 3 SD control limits is
classified as a random error. When a single random error occurs,
disregard the result. When there is an increase in the frequency of
random errors, the quality control sampling technique should be
reviewed.
Systematic Errors
A recurring measurable deviation from the mean is classified as a sys-
tematic error. One example of a systematic error is when a progres-
sive increase or decrease in control results is noted. Possible causes
are:
• aging or protein contaminated electrode
• bubbles beneath an electrode membrane
• a change in calibrant
• a change in temperature
• a change in quality control material
• aging reference electrode
If the sampling technique is acceptable and random errors continue,
refer to ELECTRODES in Troubleshooting.
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