Cumulative frequency curves

For example; Hamis has earned this much in the last 6 months.

Month	Earned (Tsh)
January	12 000
February	15 000
March	13 000
April	17 000
May	16 000
June	20 000

The first line is easy, the total earned so far is the same as Hamis earned that month. But, for February, the total earned so far is Tsh 12 000 + Tsh 15 000 = Tsh 27 000.

Month	Earned (Tsh)	Cumulative (Tsh)
January	12 000	12 000
February	15 000	27 000

For March, we continue to add up. The total earned so far is Tsh 12 000 + Tsh 15 000 + Tsh 13 000 = 40 000 or simply take the cumulative of February add that of March i.e. Tsh 27 000 + Tsh 13 000 = Tsh 40 000.

Month	Earned (Tsh)	Cumulative (Tsh)
January	12 000	12 000
February	15 000	17 000
March	13 000	40 000

The rest of the months will be: April: Tsh 40 000 + Tsh 17 000 = Tsh 57 000 May: Tsh 57 000 + Tsh 16 000 = Tsh 73 000 June: Tsh 73 000 + Tsh 20 000 = Tsh 93 000

Month	Earned (Tsh)	Cumulative (Tsh)
January	12 000	12 000
February	15 000	27 000
March	13 000	40 000
April	17 000	57 000
May	16 000	73 000
June	20 000	93 000

The last cumulative total should match the total of all earnings.

Graph for cumulative polygon is drawn with cumulative frequency on vertical axis and real upper limits on horizontal axis.

Scale: Vertical scale: 1cm represents Tsh 20 000

Give number to months. i.e. January =2, February =3 and so on

Note

To draw an Ogive, plot the points vertically above the upper real limits of each interval and then join the points by a smooth curve. Add real limit to the lowest real limit and give it zero frequency.

Class Interval	Upper Real limits (Less than)	Frequency	Cumulative Frequency
30 - 39	39.5	4	4
40 - 49	49.5	18	22
50 - 59	59.5	25	47
60 - 69	69.5	13	60
70 - 79	79.5	8	68
80 - 89	89.5	2	70