It is very much designed as a course in applied statistics, covering common topics such as types of variables and data, probability theory, hypothesis testing, measures of central tendency and ...

With a correlation that low, there will be some mean regression at work. Think of it this way. Seven door-to-door salesmen go out and sell as many vacuum cleaners as they can on a Sunday.

Regression to the mean explains that in many cases data will tend to even out—i.e., if a variable is extreme on the first observation, it will tend to be closer to the mean on the next observation.