A) What does it mean when it is said that two variables have no correlation?
When we're working with correlations, we're really asking if two variables change together. So if we say that two variables have no correlation with one another, what we're saying is that although they both may change, they don't change together. A few examples will make this clearer.
? Imagine that you sign your new puppy up for puppy classes. Since you're spending money on the classes, you would want to see a positive correlation between the number of weeks of classes you've attended and the obedience skills of your puppy. That is, you would want to see an increase in obedience skills as you saw an increase in the weeks of classes. But maybe the classes aren't very good (or maybe your puppy isn't very smart!). In that case, even though you attend classes every week, your puppy doesn't get any better at the obedience skills you ask of him. Although the amount of time you've spent in class has increased, your puppy's obedience hasn't - the two variables are not correlated.
o Think about how you could hope for the same correlation between the amount of credits you offered for a posting on Brainmass and the understanding you gained from the explanation. You would hope that as the number of credits you offered increased, your understanding would increase.
The above example(s) presented situations where you would want to see two variables increasing ...