Parameter
A parameter is a numerical property of an entire population. Parameters are typically unknown and fixed for a given population. Common parameters include μ (population mean), σ² (population variance), p (population proportion), and ρ (population correlation coefficient). Parameters are estimated using statistics calculated from samples.
Real World
The Office for National Statistics cannot measure every UK household's income, so it surveys around 20,000 households and uses the sample mean to estimate the true population mean income μ.
Exam Focus
Use Greek letters (μ, σ², p) for parameters and Roman letters (x̄, s², p̂) for statistics to show clear understanding.
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