7th Grade Math

Mean, Median, and Range

Obj. 5b

Central Tendency

When you have a “set of data” (or numbers), there are 2 different

ways you can find the center of the data.

1) Mean2) Median

Let’s look at these 2 different ways to find the center using the following…

Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4

Mean

Mean = Average

What is the Mean?

The Mean is the average.2 simple steps will give you the mean of a set of

numbers.

Mean = Average

Your report card has an average on it.

Step 1

Add the numbers.

Step 2

Divide by the # of items in the dataset.

Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4

Add the numbers: 2 + 3 + 1 + 1 + 0 + 1 + 2 + 4 =

Divide by total items: 14 ÷ 8 =

Mean

Step 1

Add the numbers.

Step 2

Divide by the # of items in the dataset.

14

Example of Mean:

1.75

Media

nMedian = Middle

What is the Median?

The Median is the middle number. How do you find the Median?

Median = Middle

ORDER

the numbers.

If there is just 1 middle #:

your done!

If there are 2 middle #’s

FIND

the middle #.Average the 2

middle numbers.

ORDER

the numbers.

If there is just 1 middle #:

your done!

If there are 2 middle #’s

FIND

the middle #.Average the 2

middle numbers.

Add the 2 middle numbers

Then, Divide by 2

Example of Median

Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4

Arrange in order: 0, 1, 1, 1, 2, 2, 3, 4

1 + 2 = 3 3 ÷ 2 =

Median

1.5

Range

Range = Biggest – Smallest

What is the Range?

The Range is not a form of central tendency, but it is another way to get information from a “set of numbers”.

The range describes the spread of the dataset.

The Range is the difference between the biggest number and the smallest number.

Range = Biggest - Smallest

Example of Range

Range = Biggest – Smallest

Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4

Subtract: 4 – 0 =

Range

4

Remember....

Mean =

Median =

Range =

Middle

Average

Biggest – Smallest

You Try!

Mandy’s math test scores:90, 85, 80, 70, 90, 65

Determine the following:

Mean _______Median _______Range _______

Answers!

Mandy’s math test scores: 90, 85, 80, 70, 90, 65

65 70 80 85 90 90

Mean __80___Median __82.5_ (find average of 80 & 85)

Range __25___

Closure

What did we learn today (key words):

Mean = _________________ ? Median = _________________ ?Range = _________________ ?

Which central tendency requires you to first put the numbers in order?

When finding the median, what do you do if there are 2 middle numbers?

Average

MiddleMostBiggest – Smallest

Average the two middle numbers by adding them together and dividing by 2.

Median