Random error affects the precision of a test (reproducibility). Some things that could cause random errors are
- bubbles in reagents or reagent lines;
- instrument instability;
- temperature variations; and
- Operator variability, such as variation in pipetting.
Systematic error causes inaccurate results that are consistently low or high. Some things that could cause systematic errors include
- change in reagent lot;
- change in calibration;
- assigning the wrong calibrator values;
- reagents that were improperly prepared or are deteriorating;
- pipettor maintenance error (not adjusted correctly or misaligned); and/or
- a deteriorating photometric light source in the instrument.
