Intelligence tests are used in a variety of settings such as schools, clinics, and courts to assess the intellectual capacity of individuals of all ages. Intelligence tests are used to make high-stakes decisions such as special education placement, employment, eligibility for social security services, and determination of the death penalty. Considering the importance of intelligence tests and the decisions for which these are used, it is imperative to ensure valid test scores. This study examined the effect of examiner errors made by graduate students on the Index and FSIQ scores using the most recent versions of the Wechsler Intelligence test Scales: WAIS-IV and WISC-V. This study also aimed to document the change in qualitative descriptors for the FSIQ after corrections to compare the prevalence of errors between the WAIS-IV and WISC-V, and to determine if the total number of errors decreased from the first to the last record form submitted by student examiners. The Wechsler Intelligence scales continue to lead among school psychologists, psychiatric psychologists, and neuropsychologists in their practice and study and have been found to be among the most often employed tools for evaluating children's intellectual abilities and particular strengths and weaknesses. Results suggested that errors continue to persist over time. The effect of errors on the derived scores and changes in qualitative descriptors appeared to be rare. Results also suggested that errors by graduate students were more prevalent on the WISC-V record forms compared to WAIS-IV record forms. Although students continued to make an average of eight errors on their last record form, errors reduced significantly from students' first to their last record form. The findings of this study may be most helpful for instructors and graduate students in training. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]