Question

Find the cumulative frequencies for each class, and place the results in the third column.

Answer 1

The frequency distribution of systolic blood pressures is given as follows:

Boundaries	Frequency
89.5 – 104.5	24
104.5 – 119.5	62
119.5 – 134.5	72
134.5 – 149.5	26
149.5 – 164.5	12
164.5 – 179.5	4
	200

 

We are supposed to find the cumulative frequencies for the given frequency distribution. The cumulative frequencies are obtained by adding the numbers in the frequency column up to that particular limit and place in the third column.

 

Example:

For the first class, the cumulative frequency would be the frequency itself, that is, 24. For the second class, the cumulative frequency is the sum of frequencies up to that class. That is, 24+62 = 86.

 

For the third class, it would be 24 + 62 + 72 = 158 and so on.

 

The following table gives the cumulative frequency of the given distribution.

 

Boundaries	Frequency	Cumulative Frequency
89.5 – 104.5	24	24
104.5 – 119.5	62	86
119.5 – 134.5	72	158
134.5 – 149.5	26	184
149.5 – 164.5	12	196
164.5 – 179.5	4	200
	200

 

We can see that the last cumulative frequency is the sum of all frequencies.

We can see that the last cumulative frequency is the sum of all frequencies.