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Poll says 52% ± 3% (95% CI for proportion). That means the true population proportion is between 49% and 55% with 95% confidence. 8. Linear Regression: Measuring Relationships We want to model $Y$ (response) as a linear function of $X$ (predictor).
For population mean $\mu$: $$\barx \pm t^* \cdot \fracs\sqrtn$$ Statistics For Dummies
Significance level $\alpha$ = P(Type I error). Power = 1 − P(Type II error). Instead of a single “best guess,” give an interval likely to contain the true parameter. Poll says 52% ± 3% (95% CI for proportion)
This is crucial for medical tests, spam filters, and machine learning. Linear Regression: Measuring Relationships We want to model
“95% CI” means that if we repeated the sampling process many times, 95% of those intervals would contain the true $\mu$. Not “probability that $\mu$ lies in this interval” — $\mu$ is fixed, interval is random.

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