How to draw and use…..

How to draw and use….. Cumulative frequency graphs

Cumulative frequency is just… A running total

Look at these tables

Once we have calculated thecumulative frequency We don’t need the frequency any more.

We can use our results to drawa cumulative frequency curve Along the ‘x’ axis Up the ‘y’ axis

Plot the points 44 40 36 32 28 24 20 16 12 8 4 0 Cumulative frequency 0 5 10 15 20 25 30 35 40 45 50 55 60 Age (years)

Draw the curve 44 40 36 32 28 24 20 16 12 8 4 0 Cumulative frequency 0 5 10 15 20 25 30 35 40 45 50 55 60 Age (years)

Now draw in the median • Remember it is halfway up the cumulative frequency axis – in this case 22

Median…… 44 40 36 32 28 24 20 16 12 8 4 0 Cumulative frequency halfway up Read off here 0 5 10 15 20 25 30 35 40 45 50 55 60 Age (years)

The median is …….. (about) 26.

Now for the lower quartile Quarter of the way up the Cumulative frequency axis

Lower Quartile 44 40 36 32 28 24 20 16 12 8 4 0 11 – quarter of 44 Cumulative frequency Read off here 0 5 10 15 20 25 30 35 40 45 50 55 60 Age (years)

So the lower quartile is …. 19

Upper quartile Three quarters of the way up the Cumulative frequency axis

Upper quartile 33 – three quarters of 44 44 40 36 32 28 24 20 16 12 8 4 0 Cumulative frequency Read off here 0 5 10 15 20 25 30 35 40 45 50 55 60 Age (years)

The upper quartile is …. 32

Inter-Quartile range Upper quartile – lower quartile

Upper quartile – lower quartile 32 - 19

Inter-quartile range = 13

Try this one …..

How to draw and use…..