Decimal answers (impossible answers)

The mean value is sometimes an 'impossible' number.

Example    A football team has a mean score of 2.4 goals in a month.
                    But you can't have 0.4 of a goal!

Example    The mean family size in a town is 4.5
                    But we can't have 0.5 of a person!

These real-life mean value averages often don't make sense as the answer is not a whole number. Let's look at an example:

Example    In a college there are four classes of numeracy students. The number of students in each class is 11, 13, 14 and 16. What is the mean number of students in a class?

To work out the mean number of students in a class find the total number of students and divide by the number of classes.
The total number of students is 11 + 13 + 14 + 16 = 54
There are 4 classes, so divide the total by 4, 54 ÷ 4 = 13.5
The mean number of students in a class is 13.5

You can't have 0.5 of a student, but this is still the mean value. You could call it an impossible number in this case.

But, you could still use this number to make calculations. For example, if you know that the mean class size is 13.5 students then you could estimate that in 10 classes there would be 10 x 13.5 = 135 students.