Stem-and-Leaf Plot

1
Stem-and-Leaf Plot

• 7th Pre Algebra
• Lesson 11-2

2
What is a stem-and-leaf plot?

• A T-chart that is used to show numeric data and
  the distribution of numbers

3
Why would I want to use one?

• It displays a lot of numbers in a neater,
  cleaner, and organized way.
• It makes it easier to see how spread out the
  numbers are
• It is easier to identify outliers

4
Reading a Stem-and-Leaf Plot(how to analyze
and make inferences)
5
Things you need to know

• Stems
• The stems include the digits in the tens place
  and higher (sometimes the units place too, if
  data includes decimals)
• The top of the stem includes all but the last
  digits of the smallest number
• The bottom of the stem includes all but the last
  digit of the largest number
• Your stems need to include ALL consecutive
  numbers in betweeneven if there is no data for
  it.

6
Things you need to know

• leaves
• The leaves are always from the LAST digit from
  your data (usually ones place)
• The leaves need to be organized from least to
  greatest
• You can have multiples of the same digit per line
  (interval)

7
What does it look like?
The stem-and-leaf plot below shows the number of
students enrolled in a dance class in the past 12
years.                                         
The number of students are 81, 84, 85, 86, 93,
94, 97, 100, 102, 103, 110, and 111.
8 4 means 84
8
Should I skip numbers in my stem?
You HAVE TO include all of the consecutive
numbers from the first stem until the last
one. Notice how 6, 7, and 10 have no data next
to them. It means that no countries reported
sixties, seventies, or one hundreds of infant
deaths. You CANNOT put a zero in the leaf spot
because that implies that you have data for that
stemwhich you dont.
No!
This chart shows the number of infant deaths per
1,000 live births, of countries in Western Africa.
9
Making a Stem-and-Leaf Plot
10
This stem-and-leaf plot shows points that
students received on a science quiz.
73 75 76 78
61 64 67 67 67
40 49 49 56 58 59
80 85 87 88 92 96 100 100
Stem Leaves







4
9
0
9
6
5
9
8
6
1
7
4
7
7
7
3
6
5
8
8
0
7
5
8
9
6
2
10
0
0
11
Finding the Range, Mode,Median, and Mean
12
Range biggest number smallest number
40 is the smallest number
73 75 76 78
61 64 67 67 67
40 49 49 56 58 59
80 85 87 88 92 96 100 100
Stem Leaves







4
9
0
9
100 40 60 The range for this data set is 60
points.
6
5
9
8
6
1
7
4
7
7
7
3
6
5
8
100 is the largest number
8
0
7
5
8
9
6
2
10
0
0
This stem-and-leaf plot shows points that
students received on a science quiz.
13
Finding the Median (the middle number)
Start counting with this leaf!
73 75 76 78
61 64 67 67 67
40 49 49 56 58 59
80 85 87 88 92 96 100 100
Stem Leaves







Leaf number 12 This is the halfway point!
4
9
0
9
I have 23 leaves. If I divided that in half, I
would end up with 11.5. This means that the 12th
number is my median.
23 2 11.50 ? the 12th number will be our
median. The twelfth number is 73. This is my
median.
6
5
9
8
6
1
7
4
7
7
7
3
6
5
8
8
0
7
5
8
9
6
2
0
0
10
This stem-and-leaf plot shows points that
students received on a science quiz.
14
Finding the Mode (the number that shows up most)
You have more 7s than 9s or 0s. That means 67 is
your mode.
73 75 76 78
61 64 67 67 67
40 49 49 56 58 59
80 85 87 88 92 96 100 100
Stem Leaves







4
0
9
9
For the mode, look at each row of leaves
separately. If you see more than one of a number,
underline it. After looking at all your rows,
pick the underlined number that has the most
digits.
6
5
9
8
6
1
4
7
7
7
7
3
6
5
8
8
0
7
5
8
9
6
2
10
0
0
This stem-and-leaf plot shows points that
students received on a science quiz.
15
Finding the Mean (the average)
73 75 76 78
61 64 67 67 67
40 49 49 56 58 59
80 85 87 88 92 96 100 100
Stem Leaves







4
0
9
9
To find the mean, you will be doing a combination
of Multiplying, adding, and dividing.
6
5
9
8
6
1
4
7
7
7
7
3
6
5
8
8
0
7
5
8
9
6
2
10
0
0
This stem-and-leaf plot shows points that
students received on a science quiz.
16
Finding the Mean (the average)
Stem Leaves







We will start by adding a zero to the end of the
stem and then multiplying that number times the
number of leaves you have.
4
0
9
9
6
5
9
8
6
1
4
7
7
7
7
3
6
5
8
8
0
7
5
8
9
6
2
10
0
0
This stem-and-leaf plot shows points that
students received on a science quiz.
17
Finding the Mean (the average)
Stem Leaves







2
4
0
9
9
4
0
x 3
120
6
5
9
8
5
0
x 3
150
6
0
x 5
300
6
1
4
7
7
7
7
3
6
5
8
7
0
x 4
280
8
0
x 4
320
8
0
7
5
8
9
0
x 2
180
9
6
2
10
0
0
10
0
x 2
200
5
0
15
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Finding the Mean (the average)
Now add up all your leaves. Look around the
entire Stem-and-Leaf Plot. Try to make tens or
multiples of five. This will make it easier for
you to add quickly.
Stem Leaves







4
0
9
9
4
0
x 3
120
6
5
9
8
5
0
x 3
150
6
0
x 5
300
6
1
4
7
7
7
7
3
6
5
8
7
0
x 4
280
8
0
x 4
320
8
0
7
5
8
9
0
x 2
180
9
6
2
10
0
0
10
0
x 2
200
5
0
15
19
Finding the Mean (the average)
10
10
Stem Leaves







10
4
0
x 3
120
4
0
9
9
X
X
10
5
0
x 3
150
6
5
9
8
X
X
X
10
6
0
x 5
300
6
1
4
7
7
7
X
X
X
X
X
20
7
0
x 4
280
7
3
6
5
8
25
X
X
X
8
0
x 4
320
8
0
7
5
8
95
X
X
9
0
x 2
180
9
6
2
X
0
x 2
200
10
0
0
10
5
0
15
117

20
Finding the Mean (the average)
We have 23 leaves. Divide your sum by 23.
Stem Leaves







4
0
9
9
6
5
9
8
1667
23
6
1
4
7
7
7
7
3
6
5
8
Mean Approximately 72.48
8
0
7
5
8
9
6
2
10
0
0
5
0
15
117