6.1.7—Descriptive statistics

Mean, median, mode, range and standard deviation summarise a dataset; each reveals a different feature.

Outliers and skew can make the mean misleading, while a summary hides individual cases.

Choose the statistic that matches the distribution and decision.

Delivery times of 2,2,3,3,20 minutes have median 3 but mean 6; the outlier matters for capacity.

A summary is not causation or a forecast.

Use the full authorized set deliberately. Mean = sum of values ÷ number of values; median is the middle ordered value; mode is the most frequent value. Quartiles split ordered data into four parts and show position and spread; standard deviation measures typical dispersion around the mean, so a larger value indicates less consistency when datasets use comparable units and scales. Bar charts compare discrete categories, pie charts show parts of a whole when totals and proportions are meaningful, and infographics communicate selected findings but can distort through scale or omission. For 2, 2, 3, 3, 20, the mean is 6 and median is 3: report the outlier and choose the summary that fits the decision.