How do you use data for investment decisions?

He (Robert Gates) wasn't an investment person, he admitted, but he asked whether the data I had just presented as a reason for my bullish outlook was data that I had selected because it supported my theory. Or was it data that I consistently tracked, hoping to detect signs of change?

from Reading Minds and Markets by Jack Ablin

I have to highlight this passage from Jack Ablin book from a few years ago. It is very important to think about whether we are using or marshaling data to support our view or whether we are drawing conclusions from data that we look at on a regular basis. The right answer is that the data tells the story, but human nature often works in reverse.