To apply rate-of-return analysis correctly, we need to classify an investment as either a simple investment or a non simple investment. A simple investment is defined as an investment in which the initial cash flows are negative and only one sign change in the net cash flow occurs, whereas a nons imple investment is an investment for which more than one sign change in the cash flow series occurs. Multiple occur only in non simple investments. However, not all nonsimple investments will have multiple i*s