Cumulative frequency is kind oflike a running total. We add each frequency to the ones before to get an 'at least' total.
These cumulative frequencies ('at least' totals) are plotted against theupper class boundaries to give us a cumulative frequency curve.
The cumulative frequency column is the column you will be expected to add for yourself.
To draw the cumulative frequency curve we simply plot the cumulative frequencies against the upper end of each class interval.
Remember to always place the cumulative frequencies on the y-axis.
The upper quartile is the 3/4 point of the graph.
The lower quartile is the first 1/4 of the graph.
The median is the middle point of the graph.
The interquartile range is the loweer quartile subtracted from the upper quartile.