Rater errors and biases are unpredictable. Different ratees may elicit different biases. Rater errors are more probable when the acceptability of the assessment tool is low (has low face validity or it is regarded as unfair). Raters will use it with less motivation or to serve their personal goals. The more standardized, objective, and reliable the assessment tool, the smaller the possible bias effect.
Rater errors and biases probably cannot avoided entirely.

How to avoid rating errors – the Dos

Evaluate on the basis of evidence only.
Be aware of possible biases. Take the Implicit Association Test to identify personal biases.
Try to be a good observer. Apply your skills from BOT (Behaviour Observation Training):
- Separate observation from judgment.
- Describe specific behaviour rather than an individual’s personality.
- Take notes and rate on the basis of documented observations of behaviour.
- Record your observations in behavioural terms.

How to avoid rating errors – the Don’ts

Do not use just a limited range of the rating scale.
Do not try to compensate for a near miss on one dimension with a generous rating on another.
Do not consider only the first or last incident. Observe and rate the whole range of behaviour over time.
Do not make comparisons with other performers; use the rating scale for the performance observed.
Do not rate people you perceive as similar to yourself more favourably.
Do not rely on your gut feelings.

Rating Task 1: Identify and avoid rating errors

The following video shows a scene from an assessment centre. Four young people apply for a trainee program. Their task is a leaderless group discussion on retail in the Internet age.

Please rate the behaviour of each person on the item: “Works well with others; understands and is attentive to their needs.”

Try to avoid the aforementioned rating errors.
Try to follow the dos & don’ts.
Use this scale:

Ask yourself whether you could avoid rating errors:

Could you avoid being too lenient, strict, or neutral when you rate? If not, go back to the rater errors section.
Could you avoid personal biases (e.g. about people of a different skin color or who are overweight)? If not, go back to the rater errors section.
Was your rating based solely on the scale and not on other characteristics (e.g. dress, accent, attractiveness, similarity to yourself)? If not, go back to the rater errors section.
Was your rating really based solely on the scale or also on comparisons among the four people? If not, go back to the rater errors section.

Rating Task 2: Identify and avoid rating errors

The following video shows three employees. They are discussing a new business idea: bicycle helmets for the Netherlands.

Please rate the behaviour of each person on the item “Challenges the status quo.”

Try to avoid the aforementioned rating errors.
Try to follow the dos & don’ts.
Use this scale:

Ask yourself whether you could avoid rating errors:

Could you avoid being too lenient, strict, or neutral when you rate? If not, go back to the rater errors section.
Could you avoid personal biases (e.g. about people of a different skin color or who are overweight)? If not, go back to the rater errors section.
Was your rating based solely on the scale and not on other characteristics (e.g. dress, accent, attractiveness, similarity to yourself)? If not, go back to the rater errors section.
Was your rating really based solely on the scale or also on comparisons among the three people? If not, go back to the rater errors section.