The area 0.00625 of variables 0 to 5 is calculated in terms of 5 divided by 800. 5 represents the number of variables while 800 for all variables involved. If we calculate the density curve from 5 to 800, this represents 795 variables. Then we need to divide 795 by 800 to get the remaining area of the density curve. This results to 0.99375, which is the are of the density curve from 5 to 800. Adding 0.00625 and 0.99375 will give a value of 1.
