Which data display is best for showing the spread and central tendency of a small data set with potential outliers?

• A. Histograms
• B. Scatter plots
• C. Box plots
• D. Bar charts

Answer: (C)

To show how spread out the data is and where the center lies, especially when outliers might be present, a box plot is ideal. It places a box around the middle 50% of the data to show the quartiles, with a line inside the box marking the median. The length of the box tells you about the interquartile range, which is a nice measure of spread for the central portion of the data. The whiskers extend to show the range of the rest of the data, and any individual points beyond the whiskers point outliers. This combination makes it easy to see both the central tendency and the overall spread while clearly highlighting outliers.

Histograms show how often data fall into bins, which can be noisy with small data sets and doesn’t clearly indicate the median or outliers. Scatter plots display relationships between two variables, not the spread and center of a single data set. Bar charts compare category values and aren’t designed for showing the spread of numeric data.