Why line graphs?
Line graphs make it easier to talk of the “area under the curve” between two points where: area = proportion (or percent) = probability That is, we could ask what proportion of our class scored between 7 & 9 on the quiz If we assume that the total area under the curve equals one, then the area between 7 & 9 equals the proportion of our class that scored between 7 & 9 and also indicates our best guess concerning the probability that some new data point would fall between 7 & 9 The problem is that in order to calculate the area under a curve, you must either: • use calculus (find the integral), or • use a table that specifies the areas associated with given values of your variable The good news is that a table does exist, thereby allowing you to avoid calculus.
