1. Mathematics
Cumulative frequency

2. The number of houses in each village in Essex were counted
The cumulative frequency is found by adding up as you go along (a running total)
Cumulative frequency curves
The number of houses in each village in Essex were counted
No. of houses
No. of villages
50 < P < 100 7
100 < P < 150 24
150 < P < 200 29
200 < P < 250 18
250 < P < 300 12
Cumulative freq.
Step 1
Work out cumulative frequencies 7 31
Step 2
Write down the
co-ordinates you are
going to plot 60 78 90
Step 3
Draw the cumulative frequency curve
Co-ordinates:
(50, 0) , (100, 7) , (150, 31) ,
(200, 60) , (250, 78) , (300, 90)
The graph will need the Cumulative Frequency on the y-axis 0  90
and No. of houses on the x-axis 0  300
All points must be joined using a smooth curve

3. Cumulative frequency curves
From your curve calculate the :
Median
Lower quartile
Upper quartile
Inter quartile range
No. of villages with
more than 260
houses in 90 80 70 60 50 40 20 30 10
100
150
200
250
300
c.f.
No. of houses
100th percentile UQ
Median LQ
Answers:
Median = 175 houses
LQ = 140 houses
UQ = 215 houses
IQR = 215 – 140
= 75 houses
>260 hs = 9 villages
140
175
215