Descriptive statistics summarize data: central tendency (mean, median, mode) and spread (variance, SD, range).
Dataset: 4,7,13,16,21,21,21,30,36,37,38 → Mean 22.18, Median 21, Mode 21.
Standard deviation measures how spread out values are from the mean.
Mean = sum ÷ count. Median = middle value when sorted. Median is more robust against outliers.