Which method of measuring relative strength involves ranking stocks based on the slope of their trend line?

The correct approach to measuring relative strength by ranking stocks based on the slope of their trend line is the trend slope method. This method focuses on assessing the angle or slope of a stock's price trend line over a specified period. A steeper slope indicates a stronger upward trend, which suggests better relative performance compared to other stocks.

By using this method, traders can systematically analyze and compare various stocks, enabling them to identify those that exhibit the strongest trends. The trend slope method helps in making informed decisions about which stocks to invest in, based on their price momentum.

In contrast, the alpha method involves comparing the excess return of an investment relative to a benchmark, the Levy method may refer to a specific statistical technique or model, and the percentage change method focuses on calculating the growth percentage from a starting point to an ending point in price, rather than analyzing the slope of a trend line. Each of these methods serves different purposes in relative strength analysis, but the trend slope method specifically emphasizes the angle of price movement, making it the appropriate choice for the question.