It's not a lie though, the distinction is subtle but important.
Something like asking you what the closing stock price for GOOG was yesterday. If you said "I think it was 500" but say it was 505, boom insta-crime.
There's been quite a few examples of the FBI then using the threat of prosecuting the above "crime" in order to get leverage so people will comply with things they may not have usually done.
You should probably read 18 USC 1001 [1]. Your example doesn't work for several reasons.
* The statement is about your belief, not the facts. If you actually believed that, it's not a false statement.
* Even if the statement is a statement of fact and not belief (e.g. "The closing stock price for GOOG was 500 yesterday."), the statement has to be materially false. 500 vs 505? Close enough.
* Even if the statement is materially false or fraudulent, (e.g. the stock price was really 50,000), the falsehood has to be given "knowingly and willfully."
