When you are '90% sure', how often are you actually right?

The range you feel 90% sure about is usually way too narrow.

Ask people for a range they are 90% confident contains the true answer and the real value still falls outside it about half the time. The honest range should be much wider than the one that feels right - our sense of certainty runs far ahead of how often we are correct.

Guess a price range you are '90% sure' a new iPhone costs in VND. Most people pick something tight like 25-30 million; the real spread of models blows past both ends.

When you feel sure, widen the range - your confidence is bigger than your accuracy.

Before you bet, commit, or promise a number, stretch your range and ask what could put the truth outside it.

90% sure feels like 9 in 10, but you are right closer to 1 in 2.

Learn the idea and practice English at the same time.