When interviewing you need to be aware of the following common errors that can lead to biases:
Attempting to rate an individual positively or negatively based on physical and personal characteristics unrelated to the person’s performance.
Halo and Horn Effect
Resist the tendency to rate the individual as good or bad based on one trait or comment. Remember that people are complicated, never wholly good or bad.
Occurs when assessors do not want to be negative or positive but instead tend to rate all people in the middle. The error in this bias is that it can result in inaccurate assessments.
Excessive Strictness or Leniency
Tendency of some assessors to rate either leniently or strictly. It is best to have clear expectations, which are then realistically evaluated.
Transferring one’s own feelings of awkwardness or contentment on the person being assessed.
Rating based on how they compare with others rather than on their own merits. A very effective person may rate less only because he/she is being compared to an outstanding person.
Assessors judge one trait assuming that it is related to another. For example, someone with quick reactions may be judged as highly intelligent although speed of reaction is not an accurate gauge of intelligence.
Tests should reflect the actual skills needed for the job, and should be a sample of the typical work that is done. For example if you are hiring for a secretary an appropriate test would be drafting a letter in response to a typical problem.