Central Tendency
4-4
Mean
The average of the data
 Steps to take to find the average

◦ 1. Add all numbers together
◦ 2. Divide that answer by how many numbers
there were in the original
Example Word Problem
Randy Johnson manages a fast-food restaurant
called Shelley’s. The head office wants to know
the average length of employment at the
restaurant. Randy compares the starting date
and ending date for every employee who left
during the last 6 months. Here is the number of
months that each of those employees worked at
Shelley’s:
Ashley – 6, Joey – 14, Mike – 8, Lisa – 3, Nick – 12,
Annie – 9, Bobby – 15, Tom – 18, Denise - 14


Step 1 – Add all numbers together
◦ 6 + 14 + 8 + 3 + 12 + 9 + 15 + 18 + 14 =
 99

Step 2 – Divide by the amount of
numbers you had
◦ 99 ÷ 9 =
◦ 11
◦ So the average length of employment at
Shelley’s restaurant was 11 months.
Examples

1. 10, 6, 9, 14, 11

2. 5, 9, 3, 12, 6, 17
Median

Gives the middle value when the numbers
are listed in order
◦ 1. put the numbers in order from least to
greatest
◦ 2. find the number in the middle
◦ 3. (if there are two numbers in the middle,
add them and divide by two)
Examples:

26, 15, 48, 53, 74, 39

4, 6, 10, 11, 6, 2, 6, 3
Mode

Value the occurs most often
◦ 1. find the number that is repeated the most
◦ 2. if no numbers are repeated, there is NO
MODE
◦ 3. if there are multiple numbers that are
repeated the same amount of times, they
both/all are the mode
Examples:

1. 46, 3, 57, 89, 2, 17, 101, 33

2. 19.4, 89.6, 75.34, 19.4, 0.01, 89.6
Range

Shows how much the data varies and is
the difference between the greatest
number and the least number
◦ 1. take the biggest # and subtract the
smallest #
Examples:

1. 45, 79, 21, 86, 55, 94

2. 4, 6, 10, 11, 6, 2, 6, 3
Outlier
The outlier is a data value that is much
greater or much less than the other data
values
 An outlier WILL affect the mean of a
group of data
 Ex. 4, 3, 7, 29, 2, 5
 The outlier is 29 because it is much bigger
than the rest of the numbers
