Be the Professor - Mean, Median, and Mode

Hello, my I am Professor Kilmartin and today I will be teaching you how to calculate mean, median and mode.

Vocabulary:
set = a sequence of numbers
mean = average of numbers in set
median = the number in the middle spot of the set when the numbers are in order from least to greatest
mode = the number that appears the most in the set

Let's use an example to help you understand how to calculate these three things.

Example One:

Ages of Students in a Small Elementary School (Grades 1-4)

9, 9, 7, 8, 8, 6, 7, 8, 6, 6, 7, 8, 9, 8, 8, 9, 6

First, put numbers in order from least to greatest

6, 6, 6, 6, 7, 7, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9

MEDIAN

Once the numbers are in order, you can calculate the median by counting from the edges of the sequence until you get to the middle number. In this example, you do not have a single middle number. You get two 8's, so you calculate the number between that, which is just 8. In a different example you will be able to understand this better.

MODE

Next, to find mode, you count up how many times each number comes up in the set. Whichever one appears the most is the mode.

6 = 4 times
7 = 3 times
8 = 6 times
9 = 4 times

8 is the mode because it shows up most in the set.

MEAN

Finally, to calculate the mean. It has a good amount of steps so I'll list them out for you.

1.) Add up all the numbers in the sequence
2.) Divide that by the number of numbers in the set
3.) That's the mean!

6+6+6+6+7+7+7+8+8+8+8+8+8+9+9+9+9=129

129 / 17 = 7.58823529

The mean is approximately 7.58.

Example Two:

Average of Test Scores
50, 80, 75, 90, 100, 70

First, put numbers in order

50, 70, 75, 80, 90, 100

MEDIAN

One the numbers are in order, count from the edges of the sequence until you get to the middle number. In this case we dont have a middle number. We get 75 and 80, so we calculate the middle number between, which comes out to be 77.5.

The median is 77.5

MODE

There is no mode in this set, because each number only shows up one time.

MEAN

Add up all the numbers

50+70+75+80+90+100= 465

Divide

465/6 = 77.5

The mean is 77.5

TRICKS:

If you have trouble figuring out what the difference is between mean, median, mode, just remember this rhyme. It follows the tune of the nursery rhyme, Three Blind Mice.

Mean, Median, Mode,
Mean, Median Mode,
Central tendency,
Central tendency,
Mean's the average of the lot,
Median's the one in the middle spot,
Mode's the one you see a lot,
Mean, Median, Mode.

By learning this simple rhyme, you will always know what mean, median, and mode are.