Ben Bernanke encountered a heavy dose of skepticism and doubt here this weekend.

In a highly anticipated speech on monetary policy Friday, the Federal Reserve chairman argued that the Fed’s easy-money policies were helping the weak economy and laid the groundwork for more action.

But economists and central bankers wondered more openly than usual if the Fed had the tools to fix the problems of the day and expressed frustration that four years of super low interest rates and extraordinary money-pumping by the Fed hadn’t done more to spur the slow-moving economy.

“Why is it that we’ve had such incredibly accommodative monetary policy for so long and we’ve had so little growth?” Donald Kohn, a Brookings Institution scholar, asked from the audience after a panel discussion here Saturday.