1. Name ___________________________________ Date __________________
Mrs. Labuski / Mrs. Portsmore Period __________ Unit 12 Lesson 4 Measure of Center
TB 6-2/6-3 OC 7-2
VOCABULARY DEFINITION EXAMPLE
MEASURE
OF CENTER
A single number used to
describe a data set.
RANGE
The difference between the
least and greatest values in
the set of numbers.
2,5,3,6,9,8
9 – 2 = 7
Range = 7
MEAN
The sum of all the items,
divided by the number of
items in the set. Also called
the average.
2,4,3,6
2 + 4 + 3 + 6 = 15
15 ÷ 4 = 3.75
Mean = 3.75
MEDIAN
The middle value when the
data are in numerical
order. If there are two
numbers in the middle,
find the mean (average) of
those two numbers.
2,4,3,6,8,5
2,3,4,5,6,8
4+5=9
9÷2=4.5
4.5 = median
2,4,3,6,8,5,7
2,3,4,5,6,7,8
5 = median
OUTLIER
An outlier is a value in a
set of data that is much
greater or much less than
the other values.
22, 23, 28, 54, 25
54

2. When do I know which measure of center to use?
Measure Most appropriate when….
mean •the data have no extreme values
median •the data have extreme values
•there are no big gaps in the middle of the data
Take a look at the data below.
Day of week Monday Tuesday Wednesday Thursday Friday
# of minutes spent
on homework
47 42 45 46 10
The outlier is ____10______ because it is much _smaller_ than the other numbers.
Let’s see how the outlier affects the mean, median, and mode.
Which do you think would best describe the data? Mean or Median? median
With the outlier: Without the outlier: Amount of
Change
Mean ___38____ Mean ___45____ 7
Median __45_____ Median __45.5_____ 0.5
Which is most affected by the outlier? ___mean____________________________
When an outlier affects the mean or median, choose a value that best describes the data. Which
best describes the set of data above? ___median______

3. The monthly earnings of several teenagers are $200, $320, $275, $250,$750, $350, and $310.
Find the mean.
Write the data values in order from least to greatest and find the median.
200 250 275 320 350 750
The mean and the median differ by about $ 40 . Why?
The mean is affected by the data value 750, which is much greater than the values because
of the value 750. The median is a more central value.
Which measure of center better describes a typical teenager's monthly earnings—the mean or
the median? Explain.
Median; sample explanation: The mean is greater than all but one of the data values
because of the value 750. The median is a more central value.
TRY THIS!
Luka's final exam scores for this semester are 70, 72, 99, 72, and 69. Find the mean and median.
Which is a better description of Luka's typical exam score?
Mean = 76.4; median = 72; median
REFLECT
Luka's parents ask Luka how his final exams went. Luka says, "My average exam score was
about 76." Is Luka being truthful? Is Luka misleading his parents? Explain.
He is being truthful because his mean score really is about 76. However, all but one of his
scores are less than 76, so he is misleading his parents.
Name ___________________________________ Date __________________

4. Mrs. Labuski / Mrs. Portsmore Period __________ Unit 12 Lesson 4 Measure of Center
TB 6-2/6-3 OC 7-2
VOCABULARY DEFINITION EXAMPLE
MEASURE OF
CENTER
RANGE
2,5,3,6,9,8
MEAN
2,4,3,6
MEDIAN
2,4,3,6,8,5
2,4,3,6,8,5,7
OUTLIER
When do I know which measure of center to use?

5. Measure Most appropriate when….
mean •the data have no extreme values
median •the data have extreme values
•there are no big gaps in the middle of the data
Take a look at the data below.
Day of week Monday Tuesday Wednesday Thursday Friday
# of minutes spent
on homework
47 42 45 46 10
The outlier is __________ because it is much ___________________ than the other numbers.
Let’s see how the outlier affects the mean, median, and mode.
Which do you think would best describe the data? Mean or Median? ______________
With the outlier: Without the outlier: Amount of
Change
Mean _______ Mean _______
Median _______ Median _______
Which is most affected by the outlier? _______________________________
When an outlier affects the mean or median, choose a value that best describes the data.
Which best describes the set of data above? ________________________

6. The monthly earnings of several teenagers are $200, $320, $275, $250,$750, $350, and $310.
Find the mean.
Write the data values in order from least to greatest and find the median.
________________________________________________
The mean and the median differ by about $ _______________. Why?
_____________________________________________________________________________
_____________________________________________________________________________
Which measure of center better describes a typical teenager's monthly earnings—the mean or
the median? Explain.
_____________________________________________________________________________
_____________________________________________________________________________
Luka's final exam scores for this semester are 70, 72, 99, 72, and 69. Find the mean and median.
Which is a better description of Luka's typical exam score?
Luka's parents ask Luka how his final exams went. Luka says, "My average exam score was
about 76." Is Luka being truthful? Is Luka misleading his parents? Explain.
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________

7. The monthly earnings of several teenagers are $200, $320, $275, $250,$750, $350, and $310.
Find the mean.
Write the data values in order from least to greatest and find the median.
________________________________________________
The mean and the median differ by about $ _______________. Why?
_____________________________________________________________________________
_____________________________________________________________________________
Which measure of center better describes a typical teenager's monthly earnings—the mean or
the median? Explain.
_____________________________________________________________________________
_____________________________________________________________________________
Luka's final exam scores for this semester are 70, 72, 99, 72, and 69. Find the mean and median.
Which is a better description of Luka's typical exam score?
Luka's parents ask Luka how his final exams went. Luka says, "My average exam score was
about 76." Is Luka being truthful? Is Luka misleading his parents? Explain.
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________