An effective method of measuring the performance of a stock is to compare the return on that stock with a world market index. the CPI. the London Interbank Offered Rate (LIBOR). an index of stocks that represents similar firms. Choose the correct answer below. Buying stock on margin is when an investor buys and sells a stock on the same day and uses the profit to purchase a new stock at a lower value. Buying stock on margin is when an investor purchases a stock for a lower price than market value. Buying stock on margin is when an investor purchases a stock with a small amount of personal funds and borrows the remainder of the funds from the brokerage firm. Buying stock on margin is when an investor sets a condition to buy a stock when the price falls to a specific level