Which graph plots cumulative frequencies and uses running totals?

• A. Bar chart
• B. Ogive
• C. Histogram
• D. Pie chart

Answer: (B)

The concept being tested is cumulative frequencies, which are running totals of how many observations fall at or below a given value. The graph that represents these running totals as a continuous curve is the ogive, or cumulative frequency curve. You construct it by calculating the cumulative frequency up to each class boundary (for a less-than ogive, plot upper class boundaries against the cumulative totals). The line starts at zero and ends at the total number of observations, showing how the count builds as you move up the values. This makes it especially handy for reading percentiles and medians—you can find the value corresponding to a desired cumulative frequency by locating it on the vertical axis and tracing to the curve. Other graphs like bar charts, histograms, and pie charts display frequencies per category, per class, or proportions of the whole rather than running totals, so they don’t plot cumulative frequencies.