Distributions, center and spread

Explore distributions, center, and spread through numerical data, frequency tables, a dot plot, and a histogram. This precalculus extension quiz develops mean, median, range, interquartile range, and clearly specified population and sample variance. Single-select and multiselect problems progress from reading a display to comparing distributions and reasoning about changes of units. Worked explanations distinguish what a summary reveals from what it leaves unknown. Quartile conventions and variance denominators are stated wherever needed, so the emphasis stays on statistical reasoning rather than hidden conventions.