Which data display is best for showing the distribution of a single quantitative variable across a range?

• A. Line graph
• B. Scatter plot
• C. Histogram or box plot
• D. Pie chart

Answer: (C)

Showing how a single quantitative variable is distributed across its range is best done with a histogram or a box plot. A histogram groups values into bins and counts how many observations fall into each bin, so you can see the overall shape of the data—whether it’s symmetric or skewed, whether there are multiple peaks, how spread out the values are, and if there are gaps or extreme values. A box plot condenses the distribution into the median, quartiles, and overall spread, highlighting symmetry or skewness and flagging outliers.

Line graphs track changes over an ordered axis like time, so they emphasize trends rather than distribution across the value range. Scatter plots show relationships between two variables, not the distribution of a single variable. Pie charts display parts of a whole and are best for categorical data, not for showing how a quantitative variable is spread.