Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Stocks jumped today as new Federal Reserve Chairwoman Janet Yellen gave her first remarks to Congress, indicating that she will stay the course on the stimulus taper. As a result, the Dow Jones Industrial Average (^DJI 0.12%) finished up 193 points, or 1.2%, while the S&P 500 and Nasdaq both closed up more than 1% as well.

In her comments, Yellen said she understands that the economy has not fully recovered: "By a number of measures our economy is not back, the labor market is not back, to normal. There's a great deal of slack in the labor market still." Yellen also said she would focus on reducing long-term unemployment, which spiked to extraordinary highs after the financial crisis, and still remains elevated. The new chairwoman seemed to hit all the right notes in her first appearance, as stocks climbed throughout the day following her comments before the House Financial Services Committee this morning.

Stocks making noise today included Groupon (GRPN 0.76%), which finished down 6% after its top product executive, Jeff Holden, said he will leave the company March 18. The timing, coming just a week ahead of the daily-deals specialist's earnings report, struck some investors as odd, perhaps signaling poor performance in the fourth quarter. Groupon said Holden was leaving for another unnamed company, but one that's not a Groupon competitor. The sell-off may just be a jittery reaction to a stock that's made investors dizzy since its 2011 IPO, losing more than 90% of its value at one point, but stability seems to be finally arriving, as the stock has recovered since founder Andrew Mason's departure. We'll learn more when Groupon reports earnings next Thursday. Analysts are expecting an adjusted profit of $0.02 a share.

Moving in the opposite direction was iRobot (IRBT 1.06%), as shares finished up 11% after the Roomba-maker was recognized by the Patent Board for "having one of the top patent portfolios overall within the competitive electronics and instruments industry. iRobot was ranked No. 5 overall, No. 2 in "Science Strength," and No. 3 in "Industry Impact." The Patent Board put iRobot ahead of several major electronics makers, and the report is not only a feather in the tech company's cap, but also a reminder that its future products may more than justify the current high price tag even as top-line sales have slowed.