This study investigates the relationships between supervisor assessments and internship students' self-assessments for 15 workplace competencies, demonstrated in an internship or cooperative work environment. The 15 workplace competencies were developed by Iowa State University in collaboration with over 200 constituents comprised of Iowa State University COE alumni, engineering employers, COE faculty, partnering international faculty, and COE students, to provide clear, independent, and assessable measures for the eleven learning outcomes identified in the ABET Criterion 3 (a-k) outcomes. The study investigated workplace competency assessment data collected over ten years, commencing with the fall 2001 internship assessment term and concluding with the fall 2011 assessment term. The study used three separate methodologies to analyze workplace competency assessments in the COE. Part 1 analyzed data across the fifteen workplace competencies, and across ten programs in the College of Engineering, that have been involved with the workplace competency assessment of internship and cooperative students from the beginning of data collection in 2001. Supervisor assessment ratings were compared to internship student self-assessment ratings across the ten-year span from 2001-11using the non-parametric equivalent of the paired t-test; the Wilcoxon singed rank test for paired data. Part 2 of the study investigated the relationship between supervisor and student self-assessment data across assessment terms related to the 2001-05 and 2006-11 ABET accreditation cycles. The third part investigated how data tracking workplace competency strengths and weaknesses and ABET outcomes achievement percentages have changed between the assessment terms across accreditation cycles. Part 3 included an on-line survey sent to program curriculum committee members involved with workplace competency assessment data that investigated how the engineering programs are utilizing this data in support of continuous improvement of the program curricula. Results of the analysis demonstrate how paired supervisor assessment and student self-assessment ratings for assessment of the internship students' demonstration of workplace competencies can be useful in evaluating student demonstration of competency in COE learning outcomes through the experiential learning environment, and support continuous improvement practices for program curriculum development.