1. Reliable. Your measure must be consistent, giving similar results when it’s used under similar conditions. 2. Valid. To the extent that it’s possible to know this, you want to try to ensure that...

1. Reliable. Your measure must be consistent, giving similar results when it’s used under similar conditions.

2. Valid. To the extent that it’s possible to know this, you want to try to ensure that your measure measures what it’s supposed to.