Example of Class Midpoint, Relative Frequency, Cumulative Frequency
|
Interval |
Frequency |
Class Midpoint |
Relative Frequency |
Cumulative Frequency |
|
6.30-under 6.50 |
1 |
|
|
|
|
6.50-under 6.70 |
3 |
|
|
|
|
6.70-under 6.90 |
12 |
|
|
|
|
6.90-under 7.10 |
18 |
|
|
|
|
7.10-under 7.30 |
16 |
|
|
|
|
7.30-under 7.50 |
9 |
|
|
|
|
7.50-under 7.70 |
1 |
|
|
|
|
Totals |
60 |
|
|
|
Now compute the Class Midpoint, which is the average of the two class endpoints.
Class Midpoint = Class Beginning Point + 0.5 * (Class Width)
|
Interval |
Frequency |
Class Midpoint |
Relative Frequency |
Cumulative Frequency |
|
6.30-under 6.50 |
1 |
6.40 |
|
|
|
6.50-under 6.70 |
3 |
6.60 |
|
|
|
6.70-under 6.90 |
12 |
6.80 |
|
|
|
6.90-under 7.10 |
18 |
7.00 |
|
|
|
7.10-under 7.30 |
16 |
7.20 |
|
|
|
7.30-under 7.50 |
9 |
7.40 |
|
|
|
7.50-under 7.70 |
1 |
7.60 |
|
|
|
Totals |
60 |
|
|
|
Relative Frequency is the individual Class Frequency divided by the Total Frequency.
|
Interval |
Frequency |
Class Midpoint |
Relative Frequency |
Cumulative Frequency |
|
6.30-under 6.50 |
1 |
6.40 |
0.017 |
|
|
6.50-under 6.70 |
3 |
6.60 |
0.050 |
|
|
6.70-under 6.90 |
12 |
6.80 |
0.200 |
|
|
6.90-under 7.10 |
18 |
7.00 |
0.300 |
|
|
7.10-under 7.30 |
16 |
7.20 |
0.267 |
|
|
7.30-under 7.50 |
9 |
7.40 |
0.150 |
|
|
7.50-under 7.70 |
1 |
7.60 |
0.017 |
|
|
Totals |
60 |
|
1.000 |
|
Finally the Cumulative Frequency, which is the Class Interval Frequency plus the Cumulative Frequency of the preceding Class Interval, is calculated.
|
Interval |
Frequency |
Class Midpoint |
Relative Frequency |
Cumulative Frequency |
|
6.30-under 6.50 |
1 |
6.40 |
0.017 |
1 |
|
6.50-under 6.70 |
3 |
6.60 |
0.050 |
4 |
|
6.70-under 6.90 |
12 |
6.80 |
0.200 |
16 |
|
6.90-under 7.10 |
18 |
7.00 |
0.300 |
34 |
|
7.10-under 7.30 |
16 |
7.20 |
0.267 |
50 |
|
7.30-under 7.50 |
9 |
7.40 |
0.150 |
59 |
|
7.50-under 7.70 |
1 |
7.60 |
0.017 |
60 |
|
Totals |
60 |
|
1.000 |
|
