Intelligence tests have been used in the United States since the early 1900s for assessing soldiers during World War I (Kaufman & Harrison, 2008; White & Hall, 1980). Presently, cognitive assessments are used in school, civil service, military, clinical, and industry settings (White & Hall, 1980). Although the results of these assessments can significantly impact an individual, a large number of administration and scoring errors occur. The rate of errors is so high that researchers have called errors in assessment "the norm" (Oak et al., 2019). Many evaluators are trained in intelligence assessment via their graduate school training. This study focused on the errors graduate students commit on the Wechsler Intelligence Scale for Children-Fifth Edition (WISC-V) and Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV). The researcher examined WISC-V and WAIS-IV protocols from masters' and doctoral students to determine if there are differences in errors between the groups. Additionally, the study reviewed the trickle-down errors made by graduate students on the WISC-V and WAIS-IV. Results suggest that master's student commit more initial item-level and trickle-down errors than doctoral students. The error pattern for initial raw, scaled, and standard score errors is similar based on degree program. One error has the potential to cause an average of 3-5 trickle-down errors. No index score was immune from graduate student errors. The FSIQ was altered by up to 62 points. Graduate training programs, graduate students, and practitioners should make efforts to reduce errors in their administration and scoring procedures. [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.]