Stats Labs

Test a claim about a population proportion using WIN/Gallup survey data on religious identification in the U.S. Build individual confidence intervals, then run a two-proportion z-test to compare 2005 with 2024.

Explore what data looks like before you summarize it. Work through variables, cases, and data types with interactive examples from the BRFSS dataset.

Compute and interpret measures of center, spread, and shape. Build histograms, boxplots, and summary tables step by step.

Classify variables, then build and read the plots that suit them. Compare group separation across dot plots, boxplots, and bar charts using a 400-case volunteer dataset.

Walk through the normal distribution from z-scores to probabilities. Adjust the curve, shade regions, and see how the empirical rule works in practice.

Draw samples from a full population and watch the sampling distribution of the mean take shape. See the standard error shrink as sample size grows, then use pnorm() to answer questions about sample means.