AP Statistics / Unit 3: Inference for Categorical Data: Proportions
3.1 Estimators
Notes
A statistic estimates a parameter.
- Unbiased: the sampling distribution's mean equals the parameter.
- Low variability: values cluster tightly; larger samples help.
- $\hat p$ estimates $p$; $\bar x$ estimates $\mu$.
Practice
An estimator is unbiased when:
Centered on the truth.
The best way to reduce an unbiased estimator's variability:
Spread shrinks as $n$ grows.
$\hat p$ is a:
It's computed from a sample.
Ready for more? Take the Unit 3 test.