Getty ImagesFederal Reserve Board Chairwoman Janet Yellen testifying before the Senate Banking Committee last JulyWhile Fed Chairwoman Janet Yellen has generally received high marks for her public appearances before Congress, that is not to say there haven’t been missteps. Who can forget last summer’s Fed’s report on monetary policy which questioned the high stock prices for social media and biotech firms. Yellen has since shied away from that level of specificity when discussing asset prices. With that in mind, here are a few ways Yellen might catch Wall Street flat-footed during her two days of testimony on Tuesday and Wednesday. Time to get going on rate hikes Yellen would surprise markets if she said it was time to get going on rate hikes. Wall Street is starting to think the first rate hike might not even happen in 2015 after finding a dovish undertone to the minutes of the January meeting released Wednesday. The minutes showed that the Fed has two options on the table: a rate hike sooner so they can move slowly or a rate hike later followed by faster moves. The main takeaway from the summary of the discussion was that a majority on the Fed policy committee are leaning toward caution. But Yellen and her key allies could actually favor a gradual process, thinking that this would be a more orderly process. They could also be worried that rates at the zero bound are creating distortions or asset bubbles. “They could feel it’s less disruptive starting now,” said James Glassman, economist at J.P. Morgan Chase. Dollar weakness is making an impact Yellen could surprise by discussing the negative impact on the economy from the strengthening dollar. The dollar started rising against all currencies in 2014 and the trend has continued this year. A Fed rate hike is expected to push it even higher. The ICE U.S. Dollar Index DXY, +0.11% , a measure of the dollar’s strength against six rival currencies, has risen steadily from around 79 in early May 2014 to more than 94 Friday. Talking about the dollar is something the Fed tries to shy away from. “Saying the dollar’s strength is counter-productive is a quagmire they don’t want to climb into,” said Mike Englund, chief economist at Action Economics. But some economists think the negative impact of the dollar’s strength are getting harder and harder to ignore. Corporate titans “are sharpening the hatchet,” to cut back their work forces, as a result of weaker profit margins, Bethune said. A frank discussion of the dollar’s impact on the economy would help investors understand why the Fed was remaining patient, he said. If you want to audit us, go ahead Yellen would surprise members of Congress if she dropped opposition to the measure to “Audit the Fed,” as the legislation is known as. That bill would allow the Government Accountability Office to explore how the central bank reached a decision on interest rates. But a few economists think Yellen would score points by giving in. “The Fed has nothing to hide. Yellen should say if you want to pass a bill to audit us — do it,” said Adolfo Laurenti, chief international economist at Mesirow Financial. Laurenti said the Fed’s opposition is overstated. GAO reports veer between “irrelevant on one side and inconsequential on the other,” he said. Greg Robb