Unit 6: Inference for Categorical Data: Proportions

To use data from a sample to draw a conclusion about a population parameter, along with a statement of how uncertain that conclusion is.

Because p̂ varies from sample to sample (sampling variability), a single sample proportion almost never equals p exactly, so conclusions need a probability-based margin.

Confidence intervals, which estimate a parameter with a range of plausible values, and significance tests, which weigh evidence against a claimed parameter value.

The sample proportion p̂ = x/n, the number of successes divided by the sample size.

p̂ = 132/400 = 0.33.

Point estimate ± margin of error, where the margin of error equals a critical value times the standard error of the statistic.