7.10. Frequency Polygons http://www.ck12.org
Construct a frequency polygon for the data.
From the histogram, the following distribution table can be constructed:
TABLE7.19:
Bin Frequency
[ 60 − 70 ) 2
[ 70 − 80 ) 5
[ 80 − 90 ) 17
[ 90 − 100 ) 23
[ 100 − 110 ) 25
[ 110 − 120 ) 4
[ 120 − 130 ) 4Now you can calculate the midpoint of each bin by adding the 2 numbers of the interval and dividing the sum by 2.
Midpoints:60 + 70
2
=
130
2
= 65
70 + 80
2
=
150
2
= 75
80 + 90
2
=
170
2
= 85
90 + 100
2
=
190
2
= 95
100 + 110
2
=
210
2
= 105
110 + 120
2
=
230
2
= 115
120 + 130
2
=
250
2
= 125
Finally, you can plot the points on a grid and join the points with lines.