There are a number of common rater errors in performance appraisals that you should be aware of and try to avoid.

The "halo effect"

The rater gives favorable ratings to all job duties based on impressive performance in just one area.

The "pitchfork effect"

The rater has a dislike for a particular trait in an employee and tends to rate the employee's entire performance negatively.

The "central" tendency

The rater steers away from assigning extreme ratings. Both the "excellent" and the "unacceptable" categories are avoided. Employees typically rate as "average."

The "recency" error

Recent events are strongly considered when appraising performance.

"Length of service" bias

A long-term employee is assumed to be performing adequately simply because of experience.

The "loose" rater

The rater wishes to avoid conflict, and is reluctant to point out weaker areas of an employee's performance.

The "tight" rater

The rater feels that no employee can measure up to the high standards set for them; goals are typically unrealistic or unachievable and they seldom rate an employee as "excellent."

The "competitive" rater

The rater rationalizes that no one under their direct supervision should be given performance ratings any higher than they themselves receive.