Making a Line Plot
• Collect data and put in chronological order
Ex. Scores on a math test
63 68 72 74 79 80 80 83 84 84 84
85 88 90 90 90 90 93 95 95 95 97
• Determine a scale and intervals
• If you have a small range, you should probably use intervals of 1
• With larger scales, it is best to mark intervals every 2, 5, or 10 numbers.
Ex. Scores on a math test
Use a scale from 60 to 100 and intervals of 5
Making a Line Plot
• Draw a horizontal line and mark the intervals
Ex. Scores on a math test
63 68 72 74 79 80 80 83 84 84 84
85 88 90 90 90 90 93 95 95 95 97
60
65
70
75
80
85
90
95
100
Making a Line Plot
• Mark an X above the number for each data point
• If a number is repeated, place one X above the
other
Ex. Scores on a math test
63 68 72 74 79 80 80 83 84 84 84
85 88 90 90 90 90 93 95 95 95 97
X
60
X
65
X X
70
75
X
XX
X
X
X XX
X
X
X
X X
80
85
90
X
X X X
95
100
Making a Line Plot
• Count the number of data points and count the
number of X’s to make sure you plotted each
point!
Ex. Scores on a math test
63 68 72 74 79 80 80 83 84 84 84
22 data points
85 88 90 90 90 90 93 95 95 95 97
X
60
X
65
X X
70
75
X
XX
X
X
X XX
X
X
X
X X
80
85
90
22 X’s
X
X X X
95
100
Reading a Line Plot
• Understand the scale and interval
Ex. This line plot has intervals of 2, so an X that falls between
numbers would represent the median of those numbers.
An X between the 6 and 8 would represent “7”
X
0
X
X
X
2
4
X
6
X
X
X
X
X
X
8
10
X
X
12
14
16
Reading a Line Plot
Finding the Minimum
Minimum – smallest value
• The minimum is the number represented by the
first X
The MINIMUM is 1
1
X
0
X
X
X
2
4
X
6
X
X
X
X
X
X
8
10
X
X
12
14
16
Do NOT just look at the numbers on the scale.
The Minimum is NOT 0
Reading a Line Plot
Finding the Maximum
Maximum – greatest value
• The maximum is the number represented by the
last X
The MAXIMUM is 15
X
0
X
X
X
2
4
X
6
X
X
X
X
X
X
8
10
15
X
X
12
14
16
Do NOT just look at the numbers on the scale.
The Maximum is NOT 16
Reading a Line Plot
Finding the Range
Range – difference between highest value and lowest value
• Subtract the number represented by the first X
from the number represented by the last X
-
= 14
1
X
0
X
X
X
2
4
The RANGE is 14
X
6
X
X
X
X
X
X
8
10
15
X
X
12
14
16
Do NOT just look at the numbers on the scale.
The Range is NOT 16 – 0 = 16
Reading a Line Plot
Finding the Median
Median – middle number when data is arranged in
chronological order
• Cross off the first and last X. Continue crossing off
the first and last X’s until you reach the middle.
The MEDIAN is 8
X
0
X
X
X
2
4
X
6
X
X
X
X
X
X
8
10
X
X
12
14
16
Reading a Line Plot
Finding the Median
Median – middle number when data is arranged in
chronological order
• If there are 2 numbers left in the middle, the
median is the middle of those 2 numbers.
The 2 middle numbers are 7 and 8,
so the median is 7.5
X
0
X
X
X
X
2
4
6
X
X
X
X
X
8
10
X
X
12
14
16
Reading a Line Plot
Finding the Median
Median – middle number when data is arranged in
chronological order
• If you get confused crossing off the X’s, list the
numbers represented by the X’s in chronological
order and cross them off.
X
0
X
X
X
2
4
X
6
X
X
X
X
X
X
8
10
X
X
12
14
1 2 4 4 7 8 8 8 10 10 10 11 15
16
Reading a Line Plot
Finding the Mean
Mean – average
• Add all the data points and divide by the total
number of data points
• Remember to include ALL the X’s
The MEAN is 7.5Continue for all data points
1 2
X
X
Add
0
Divide
byThem
the #
+
ofUp!
X’s
2
4
X
4
7
X
4
+ + +
X
6
X
X
X
X
X
X
8
10
X
X
12
14
16
+ 8 + 8 + 8 + 10 + 10 + 10 + 11 + 15
so divide by 13
98 ÷ 13 ≈ 7.538 13≈X’s
7.5
Round if you get a long decimal