8. Positive correlation - as the number of hours driven increases, the number of miles driven also increases.
9. No correlation - the number of siblings a student has does not have a direct relationship with their grade in math class.
10. Negative correlation - as the age of a car increases, the value of the car typically decreases.
11. Positive correlation - as the number of weeks a CD has been out increases, the total sales of the CD also typically increase.
12. Positive correlation - generally, the more years a person went to school, the higher their income.
13. Positive correlation - as the number of songs downloaded on an iPod increases, the amount of memory available decreases.
14. No correlation - the amount of time spent on the computer instant messaging friends does not have a direct relationship with the number of computers in your house.
15. No correlation - the age of a house does not have a direct relationship with the number of people living in the house.