We could then represent each child on the graph with a green dot. If we did this for a lot of children we could then present the results on a simple graph like the one below. The line represents lots of green dots representing lots of children. This graph shows us that as children get older they weigh more. This finding would also mean that if we knew a child's age we could predict their weight and be right every time.
Correlation coefficients are numbers that represent the relationship between two variables.
For the moment just take my word for this, we'll get to why later. Now lets take another example. This time we have the hypothesis that as people get older they get weaker. We find out their age and then ask them to lift a barbell where we can add or subtract weight. The results are reported below.