Capital budgeting is a crucial decision for financial managers, where they evaluate long-term projects using techniques like net present value. To calculate the cost of equity, which is a key part of net present value, financial managers often use the Capital Asset Pricing Model approach. This involves estimating the firm's beta through a time-series regression, where they choose a return interval and estimation period. The study found that for estimating beta, financial managers should go with a daily return interval and an estimation period of three years or less.