Statistics Basics: Mean, Spread, and Inference
Descriptive statistics summarize a list; inferential ideas estimate uncertainty. Mixing sample and population formulas is the most common classroom mistake.
Center and spread
Mean, median, and mode describe center. Variance and standard deviation measure spread—use n−1 for samples and n for populations.
From z-scores to intervals
A z-score standardizes a value. Confidence intervals combine mean, spread, and sample size; large-n worksheets often use z critical values as an approximation.