The problem with subjective measures is the opportunity they provide for bias. Bias is the inaccurate distortion of a measurement. Although training in how to conduct performance appraisals can reduce bias, o bias often occurs when raters do not emotionally unattached while they evaluate employee remain performance. The most common rater biases include
Cross-cultural biases
The halo effect
Personal prejudice
The error of central tendency
The recency effect
Leniency and strictness bias