How might an economist gather empirical data to test the proposed relationship between money and the price level?

How might an economist gather empirical data to test the proposed relationship between money and the price level?

1) Economists do not usually develop theoretical models of the economy but only analyze summary statistics about the current state of the economy.

2) An economist would persuade the Federal Reserve to change the money supply to various levels, and observe the resulting changes in the price level.

3) Unlike researchers in the hard sciences, economists cannot study complex relationships using data.

4) An economist would look for data on past changes in the money supply, and note the resulting changes in the price level