What is an example of systematic error in testing?

The halo effect is a type of systematic error that occurs when a rater's overall impression of a person influences their evaluations of specific traits or behaviors. This bias can lead to skewed results because the evaluator may allow their positive or negative feelings about one quality to impact their assessment of unrelated qualities. For instance, if an evaluator views a student as being friendly, they might unconsciously rate them higher in other regards, such as intelligence or work ethic, regardless of actual performance.

Systematic errors, such as the halo effect, are consistent and predictable, affecting measurements in a way that deviates from true scores. This distinguishes the halo effect from other types of errors, such as random biases that vary unpredictably, which may arise from factors like fatigue or environmental distractions. These other factors tend to introduce variability rather than causing a consistent direction in error, which makes the halo effect a clear example of how systematic errors can compromise the fairness and accuracy of evaluations.