In this deck, we'll explore two powerful ways to handle grouped data: cumulative frequency graphs and box plots. You'll learn what they are, how to interpret them to find key values like the median, and how to use them to compare different sets of data.

Drawing and reading from graphs and diagrams are skills that need pen and paper. This audio deck will teach you the concepts, rules, and what to look for. For full fluency, we strongly recommend practising drawing cumulative frequency graphs and box plots from a textbook or past exam papers.

To calculate cumulative frequency, you start with the frequency of the first group. For the next group, you add its frequency to the previous cumulative frequency. You continue this process, adding each new frequency to the running total, until you reach the final group.

A cumulative frequency graph is always an S-shaped curve, sometimes called an ogive. The vertical axis shows the cumulative frequency, from zero up to the total. The horizontal axis shows the data values. A key feature is that the graph never goes down, because we are always adding to the total.