🎯 Why Confidence Intervals?
No measurement is perfect. When you calculate a mean from a sample, that mean is an estimate of the true population mean. Confidence intervals quantify the uncertainty of this estimate.
📊 Definition
A 95% confidence interval means that if we repeated sampling 100 times, about 95 of the calculated intervals would contain the true parameter value.
📐 The Basic Formula
95% CI for a mean = x̄ ± 1.96 × (σ / √n)