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