Here at Zacks, our focus is on the proven Zacks Rank system, which emphasizes earnings estimates and estimate revisions to find great stocks. Nevertheless, we are always paying attention to the latest value, growth, and momentum trends to underscore strong picks.Looking at the history of these trends, perhaps none is more beloved than value investing. This strategy simply looks to identify companies that are being undervalued by the broader market. Value investors rely on traditional forms of analysis on key valuation metrics to find stocks that they believe are undervalued, leaving room for profits.In addition to the Zacks Rank, investors looking for stocks with specific traits can utilize our Style Scores system. Of course, value investors will be most interested in the system's "Value" category. Stocks with "A" grades for Value and high Zacks Ranks are among the best value stocks available at any given moment.Interpublic Group (IPG) is a stock many investors are watching right now. IPG is currently sporting a Zacks Rank of #2 (Buy), as well as a Value grade of A.Value investors also frequently use the P/S ratio. This metric is found by dividing a stock's price with the company's revenue. Some people prefer this metric because sales are harder to manipulate on an income statement. This means it could be a truer performance indicator. IPG has a P/S ratio of 0.92. This compares to its industry's average P/S of 1.05.Finally, we should also recognize that IPG has a P/CF ratio of 9.55. This metric takes into account a company's operating cash flow and can be used to find stocks that are undervalued based on their solid cash outlook. IPG's P/CF compares to its industry's average P/CF of 13.92. Within the past 12 months, IPG's P/CF has been as high as 12.26 and as low as 8.68, with a median of 10.89.Value investors will likely look at more than just these metrics, but the above data helps show that Interpublic Group is likely undervalued currently. And when considering the strength of its earnings outlook, IPG sticks out at as one of the market's strongest value stocks.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Interpublic Group of Companies, Inc. (The) (IPG): Free Stock Analysis Report To read this article on Zacks.com click here.