-- average price of gas ... continuous. An average can come out to be any number, with a huge string of decimal places. There are no numbers it CAN'T be.
-- car's speed ... continuous. Between zero and the car's maximum top speed, there are no numbers it CAN'T be.
-- number of cars ... discrete. It has to be a whole number. There can't be a half a car or 0.746 of a car passing through.
-- number of phone calls ... discrete. It has to be a whole number. There can't be a half of a call or 0.318 of a call made.
-- salaries ... I'm a little fuzzy on this one. The employer can set a person's salary to be anything he wants it to be. If they want it to be a whole number, or ANY fraction, they can do it ... there's no number it CAN'T be. BUT ... when it comes time to actually pay him, THAT has to be a whole number of pennies. There are actually a lot of numbers that they CAN'T pay, because they can't give him half of a penny, or 0.617 of a penny.
So I'm going to say that salary is a discrete variable.
