Cummulative Frequency graph

A curve or a graph of a cummulative frequency is called cumulative frequency curve or give.

Cummulative frequency or give is used for the determination of a median, quartiles, deciles & percentage.

Median: This is a middle term. It is half of a cummulative frequency.

Quartiles:Here, the cummulative frequency is divided into four places.

Deciles: Here, the cummulative frequency is divided into ten places.

Percentiles: Here, the cummulative frequency is divided into hundred places.

Example:1 The frequency distribution of the hundred participant in a high jump competition as shown below.

Weight	20 – 29	30 – 39	40 – 49	50 – 59	60 – 69	70 – 79

1. Construct the cumulative frequency table
2. Draw the cumulative frequency curve

Solution

To construct the cumulative frequency curve, you need the class mid-point and the class boundary

Weight(kg)	Frequency (f)	Class mark (x)	Cum. freq.	Class boundary
20 – 29	10	24.5	10	19.5 – 29.5
30 – 39	18	34.5	28	29.5 – 39.5
40 – 49	22	44.5	50	39.5 – 49.5
50 – 59	25	54.5	75	49.5 – 59.5
60 – 69	16	64.5	91	59.5 – 69.5
70 – 79	9	74.5	100	69.5 – 79.5

N.B: 1^st cumulative frequency is the same as first frequency

last cumulative frequency is the same as total frequency

 Cummulative Frequency Curve

Scale: 1cm to 10 unit on cum. freq axis
2cm to 10 unit on class mark axis

 Cummulative Frequency Curve slideshow examples