Ridho Jatmiko Utama and Bekman Siagian 2025. OPTIMAL STOCK PORTFOLIO USING SINGLE INDEX MODEL (Case Study: 50 Biggest Market Capitalization listed on the Indonesia Stock Exchange for the Period January 2023 – December 2023). International Journal of Economic, Business, Accounting, Agriculture Management and Sharia Administration (IJEBAS). 5, 1 (Feb. 2025), 327–342. DOI:https://doi.org/10.54443/ijebas.v5i1.2490.