Frequency Distribution with Decimals
Here's an example showing how to set up a frequency distribution when the data include decimals:
19.55
20.75
21.28
22.02
22.51
22.55
23.75
24.03
24.24
25.17
25.19
25.7
25.91
26.13
26.13
26.32
26.33
27.01
27.13
27.55
27.57
27.79
28.17
30.46.
30.91
These values were each obtained by taking the average of 25 values randomly chosen between 0 and 50
(i.e., 625 random numbers were used).
Divide the range by the number of classes (let's use 5 in this case):
(30.91 – 19.55) / 5 = 2.272
So the class width is 2.28 (round up to the next value, in hundredths).
Here's the frequency distribution. I have also included the class boundaries, needed for the histogram, and
the midpoints. The boundaries and midpoints should not be rounded off. These midpoints work out to a
value in the hundredths; sometimes you need thousandths.
Class Limits
19.55–21.82
21.83–24.10
24.11–26.38
26.39–28.66
28.67–30.94
Frequency
3
5
9
6
2
Class Boundaries
19.545–21.825
21.825–24.105
24.105–26.385
26.385–28.665
28.665–30.945
Midpoint
20.685
22.965
25.245
27.525
29.805