Predictive validity means how good something is at predicting or guessing what is going to happen in the future based on information we have today.
Let's think about it like this: You have a crystal ball that tells you what will happen tomorrow. You can use this crystal ball to predict things like whether it will rain or how many cookies you will get for snack time.
But how do you know if the crystal ball is accurate or not? That's where predictive validity comes in. If the crystal ball correctly predicts what will happen in the future, we say it has good predictive validity. If it's usually wrong or not very accurate, we say it has low predictive validity.
Now, in our everyday lives, we use predictive validity all the time. For example, we might look at the weather forecast to decide if we need to bring an umbrella to school tomorrow. Or, we might study for a test based on our teacher's past exams, hoping that studying those will help us predict what types of questions might appear on the upcoming test.
In the same way, scientists and researchers use predictive validity to test whether a certain method or tool can accurately predict something in the future. For example, they might develop a test to see whether a patient is at risk for a certain disease. They will then check whether the test actually helps to predict which patients will get that disease in the future. If the test is accurate, we can say that it has good predictive validity.
So, predictive validity is just a fancy way of saying that we are trying to accurately predict what will happen in the future based on what we know today. It's kind of like guessing, but with science and data to back it up.