Stemplots
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An effective way to summarize univariate data (observations made on a single variable)
Used in smaller numerical data sets so that each value can be observed
The last digit/digits is the leaf and the first digit/digits is the stem
List stems vertically and then corresponding leaves horizontally in ascending order
An advertising company is concerned with how much of a 4 minute telephone
advertisement is hear. A study was done to see how long the listeners stay on the line
before they hang up. Times are as follows:
1.3 0.7 2.1 0.5 0.2 0.9 1.1 3.2 4.0 3.8
1.4 3.1 2.5 0.6 0.5 2.1 4.0 4.0 0.3 1.2
1.0 1.5 0.4 2.3 2.7 0.7 0.5
0
1
2
3
4
2345556779
012345
11357
128
000
KEY:
SHAPE:
CENTER:
SPREAD:
RANGE: ________
Consider the following data set of winning scores of conference basketball games over
the last 35 years:
129 118 124 109 104
129 98 125 97 106
111 117 112 112 116
119 110 105 128 112
101 125 83 99
112 92 102 103
106 117 129 128
126 105 102
Here, it would be better to use two digits for the stem:
08 3
09 2789
10 123455669
KEY:
CENTER:
11 01222267789
12 0455688999
SHAPE:
SPREAD:
RANGE: ________
Stemplots
Take a look at the daily protein intake for 20 competitive athletes per kg of body weight:
1.4 2.2 2.7 1.5 1.7 2.3 1.5 1.8 2.8 3.0 3.3 3.3 3.4 3.5 3.2 3.0
1.8 1.9 2.0 2.3 1.5 1.9 1.7 1.8 1.6 3.0 3.5 3.5
1 455567788899
2 2733803
3 0
In a case such as this, it is important to break up the data more specifically to get a better look at its spread:
1
1
2
2
3
3
 0-4 should appear on the first line
 5-9 should appear on the second line
4
55567788899
KEY:
CENTER:
0233
78
00233445
55
SHAPE:
SPREAD:
RANGE: ________
Back to Back Comparative Stem-Plot:
The following two data sets give time (in seconds) of tobacco exposure in G rated children’s films. The
data appeared as follows for Walt Disney Films:
10 10 10 10 11 12 13 13 15 17
25 26 27 30 32 39
The data from other films appeared as follows:
10 10 10 11 12 15 19 21 25 26 30
Other
21000
95
1
65
0
1
1
2
2
3
3
4
Disney
00001233
57
2
1
3 represents
__________ for Disney
567
02
9
AND
__________ for other
Outliers are data values which is unusually far out from the rest of the values in a data set.
0
1
2
3
4
5
6
7
8
9
55589
123589999
22446666687
888999
44556
22
1
91 would be considered an outlier in this data set
Stemplots
The Game of Greed
The Game Rules – Everyone stands. Everyone starts with a score of 3 Prior to each roll, students have the
option of (1) sitting down and keeping their accumulated points or (2) remaining standing and gambling on
the next roll. A roll of 1 causes each active (standing) player to lose their accumulated points for that
round. A roll of 2-6 results in that number being added to the score for each player still standing. The round
ends once a 1 comes up.
Record your data here:
Round 1= _____ Round 2= ______ Round 3= ______ Round 4= _____ Round 5= ____ TOTAL = _____
Record your total and your gender on the board.
Males: ________________________________________________________________________________
Females:_______________________________________________________________________________
1.
From the information above, construct a back to back stemplot for the data of game totals based on
gender. Make sure that your stemplot has a key!
2. Compare the distributions of game totals based on gender.