Here are important terms in statistics, and their definitions. These are worth knowing!
Validity is a measure of how valid your observation is. It describes how closely what you’re measuring correlates to what you want to discover—that is, how well your question is answered by the observations you’re measuring.
Reliability is how trustworthy your results are. If your data gathering techniques are suspect, then the reliability of your results will be questioned.
Representativeness measures whether a collection of data actually represents the entire population being measured, or if it instead shows a skewed image of reality.
Significance measures how certain you are that there is a correlation represented in your data.
A variable is something that varies in its value. It represents the thing you are examining.
An observation is what you register in your data set.