Which of the following measures does NOT provide insight into the profitability of an investment?

The payback period primarily focuses on the time it takes for an investment to generate enough cash flow to recover the initial investment cost. While it is a useful measure for assessing liquidity and risk, it does not directly indicate the profitability of the investment in terms of the total cash inflows over time compared to the costs.

On the other hand, net present value (NPV), accounting rate of return (ARR), and discount rate all provide insights into profitability. NPV considers the time value of money and the total expected cash flows over the life of the investment compared to the initial outlay, making it a strong indicator of profitability. The accounting rate of return measures the expected annual profit relative to the initial investment, providing a clear profitability metric. The discount rate influences NPV calculations by adjusting future cash flows to present value, also relating to profitability since a higher discount rate can significantly reduce the present value of future cash inflows.

In summary, while the payback period is useful for understanding how quickly investments can be recouped, it does not measure long-term profitability, which is why it stands out as the answer to this question.