Mark Pack

Take a map.

Take a compass.

Walk out your front door.

Wander round for a bit.

Make sure you are not looking north.

Get the map out and look at it to see how to get back home.

If you look at the map with north at the top, you are 80% likely to be a man. If you look at the map with the direction you are facing at the top, you are 80% likely to be a woman. (Honest.)

PS Got a friend and not sure if they are a man or woman? You can use this technique on them too.