Picture two urns stood on a table in front of you.
You’re given the opportunity to pick a marble from one of them, and drawing a red marble wins a prize.
The first urn has 10 marbles in it, 1 of which is red.
The second urn has 100 marbles in it, 8 of which are red.
Which urn would you choose? It doesn’t seem a tricky decision: your chances of drawing a red marble out of the first urn are greater (10%) than your chances of drawing a red marble out of the second urn (8%).