What is the method to create a cumulative frequency graph?

To create a cumulative frequency graph, plot cumulative frequencies against the upper class boundaries of data intervals.

First, organise your data into a frequency table, listing the data intervals and their corresponding frequencies. Next, calculate the cumulative frequency for each interval by adding the frequency of the current interval to the cumulative frequency of the previous intervals. This gives you a running total of frequencies up to each interval.

Once you have your cumulative frequencies, identify the upper class boundary for each interval. The upper class boundary is the highest value that can be included in that interval. For example, if your interval is 10-20, the upper class boundary is 20.

Now, create a set of axes on graph paper or using graphing software. Label the horizontal axis with the upper class boundaries and the vertical axis with cumulative frequencies. Plot each cumulative frequency at its corresponding upper class boundary.

After plotting all the points, join them with a smooth curve or straight lines. This curve is your cumulative frequency graph, also known as an ogive. It helps you to quickly see the distribution of data and to find medians, quartiles, and percentiles.

Remember, the cumulative frequency graph always starts at zero and should rise as you move to the right, reflecting the accumulation of data. This visual representation is a powerful tool for analysing data distributions in a clear and intuitive way.