Words can conceal the truth:
In an effort to add liquidity to the economy, we engaged in an aggressive monetary policy, launching an asset purchase plan to acquire Treasury securities on the open market. We had intended for this quantitative easing, which created a monetary injection into the economy, to have a simulative effect on macroeconomic activity while controlling inflationary pressures. It appears, however, that these liquidity operations might have had the unintended effect of placing downward pressure on the value of the currency.
Or reveal the truth:
We have printed too much money. Doing so has driven prices up and eroded your wealth. We made a mistake.