A bias in a performance appraisal is a subjective perspective of the evaluator that gets in the way of a fair and objective review. Several specific strategies help avoid bias, but they generally center on structuring appraisals as objectively as possible and involving multiple people in the evaluations.

Examples of Biases

Liking an employee or disliking an employee leads to glaring biases. Human nature suggests a manager would instinctively base a subjective evaluation on likeability. The halo effect, for instance, causes a supervisor to assume an employee does well at everything when he does very well at one more roles. Managers also tend to give greater weight to more recent performance, which suggests incorporating a more extensive timeline is important in overcoming bias. Comparing and contrasting one employee against another also leads to biases connected to preference for one worker over another.

Overcoming Bias

Develop a More Objective Appraisal

Employers often use score-based evaluations where managers assess employee performance on criteria such as time management, customer service and productivity. The problem with this format is that bias can encourage scores that are too high or too low. One way to make appraisals more objective is to make them more data driven.

In sales, for instance, managers normally base much of an employee's evaluation on quantitative factors such as sales volume, new customers and conversation rates. For a customer service worker, using survey scores or tracking favorable and unfavorable reviews on workers for the entire evaluation period may improve objective. Rather than a manager saying, "You aren't very helpful with customers," he could say, "You only received an 85 percent approval rating from the customer you worked with." Thus, the worker's assessment is based on measurable criteria, not subjective perspective.

Involve More People

Another strategy to eliminate the major biases of one appraiser is to involve multiple people in evaluations, according to Bloomberg Business. Some companies use a 360-degree feedback tool, where a given worker is evaluated by a combination of direct supervisors, peers, colleagues, coworkers and clients. This type of evaluation allows a worker's manager to gauge the way people in varying roles feel about the employee's performance. It is harder for a worker to object to five different people in five different roles taking issue with something. This thorough system helps guard against the uncertainty of influence from manager bias in a top-down appraisal.