This three-manuscript dissertation in practice used improvement science as the methodological approach of disciplined inquiry into a problem of practice--the discrepancy of male and female participation in engineering design-based (EDB) courses and clubs in Starr School District. Manuscript 1 centered around diagnosing the problem and delved into research on creating EDB spaces and curricula that were more inclusive to females. Manuscript 2 described the implementation of an intervention using a Plan-Do-Study-Act cycle to test a theory of improvement. This mixed-method study analyzed the changes in engineering attitudes among female middle school students before and after an EDB intervention that included social aspects, peer mentors, and 3D printing. Girls (n = 22) and boys (n = 12) in the Peer Leader/ Buddy Program participated in a six-week in-school intervention where they used the engineering design process to make an end-of-the-year gift for their buddy. Participants (N = 34) took the S-STEM survey and engaged in semi-structured interviews (n = 4) before and after the intervention. Key findings included: "An intervention with 3D printing, social interaction, and peer mentors improved engineering efficacy amongst middle school females; putting effort into making a prototype to express their relatedness to others was a positive experience for female students; participants showed a pattern of viewing engineers as someone who creates a product with a purpose." Manuscript 3 offered recommendations to enhance female attitudes toward engineering, including starting engineering education in elementary school, gearing engineering experiences toward the interest of females, and pushing EDB experiences into pre-existing groups. [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.]