Notes on Statistics

What are statistics?

Statistics are numbers that describe a set of data.

What is a set of data?

A set of data is any set of numbers that describe something. They can be grades on school tests, temperatures in Seattle throughout the year or numbers that come up on dice that you throw.

What are some statistics?

Well, let's say we rolled 2 dice 11 times and we wrote down their totals. Here they are:

  6    4    10    8    8    7    2    3    9    8    12

The maximum is the largest number: 12

The minimum is the smallest number: 2

The range of a set of data is the maximum(highest) minus the minimum (lowest) number.
In our example, the range is:
12  -  2  =  10.

The mean is the average of all the numbers. The average of the 11 numbers in our set is:
     6 + 4 + 10 + 8 + 8 + 7 + 2  + 3 + 9 + 8 + 12      77
    ---------------------------------------------   =  -- = 7
                          11                           11

The mode is the most common number in the set. It is the one that occurs most often. In our set, the mode is 8 because there are 3 of them and only one each of the other numbers.


The median is the number in the middle. You can find the middle number by crossing out the lowest number, then the highest, then the next lowest, then the next highest and so on until you have only one number left. That last number is the median.
In our case, you do the crossing out and find the median:
  6    4    10    8    8    7    2    3    9    8    12
The median number is ____.