The first column will be your date column. In the second column, put down index prices; this is the "overall market" you'll be comparing your beta against. In the third column, put down the prices of the stock for which you are trying to calculate beta. Try starting with one-month intervals. Pick a date — for example, at the beginning or end of the month — and input the corresponding value for the stock market index (try using the S&P 500) and then the stock price for that day. Try picking 15 or 30 recent dates, perhaps extending a year or two into the past. Note the index price and the stock price for each date.  The longer time frame you choose, the more accurate your beta calculation will become. Historical beta changes as you monitor both the stock and the index for a longer time. One column will be for the returns of the index; the second column will be the returns of the stock. You'll be using an Excel formula to determine the returns, which you'll learn in the following step. In the second cell of your index-return column, type an "=" (equals sign). With your cursor, click the second cell in your index column, type a "-" (minus sign), and then click on the first cell in your index column. Next, type a "/" ("divide by" sign), and then click on the first cell in your index column again. Hit "Return" or "Enter."   Since return is a calculation over time, you won't put anything in your first cell; leave it blank. You need at least two data points to calculate returns, which is why you'll start on the second cell of your index-returns column. What you're doing is subtracting the more recent value from the older value and then dividing the result by the older value. This just gives you the percent of loss or gain for that period. Your equation for the returns column might look something like this: =(B3-B2)/B2 Do this by clicking on the small square at the bottom right of your index-return cell and dragging it down to the bottom-most data point. What you're doing is asking Excel to replicate the same formula...

How would you rephrase that briefly using Vietnamese?
Tạo ba cột giá trong Excel. Nhập dữ liệu vào bảng tính. Tạo hai cột cho tỷ suất sinh lời bên phải cột giá. Bắt đầu tính tỷ suất sinh lời của chỉ số thị trường cổ phiếu. Dùng chức năng sao chép để lặp lại quá trình này cho tất cả các điểm dữ liệu trong cột giá của chỉ số. Lặp lại quá trình tương tự như trên, nhưng lần này sẽ tính lợi suất cho từng cổ phiếu thay vì chỉ số. Vẽ đồ thị cho dữ liệu. Chèn thêm đường xu hướng vào biểu đồ phân tán. Tìm hệ số cho giá trị "x" trong phương trình của đường xu hướng.