In evaluating performance, there are major concerns are over instrument validity and reliability. Formative and summative methods of evaluation each requires a different evaluation design and technique. Formative evaluation assesses the effect or quality of a treatment while the experiment is in progress. Results allow for modification of the process so that the desired end outcomes can be achieved. Summative evaluation assesses the effect or quality at the end of the treatment.

Results describe the overall outcome of the investigated variable because it is an end assessment process or an after-the-fact procedure. Formative evaluation methods are intended to identify weaknesses or deficiencies that hinder the quality and effectiveness of work and to make modifications while the process is in progress. Those evaluating performance should approach the task objectively. Unfortunately, personality conflicts and appraiser styles can obscure objectivity. Appraisers who display a dominant-warm style promote consistently high outcomes from subordinates.