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LearnEdexcelYMA012018 specificationWST03 · Statistics 3Sampling

WST03 · Module

Sampling

2 subtopics≈ 70 min in total

Start the module: Sampling and unbiased estimates Open graphing calculator

Sampling and unbiased estimates
We usually can't measure a whole population, so we measure a random sample and estimate. The sample mean estimates $\mu$ fairly, but for the variance we divide by $n-1$ , not $n$ , to stop the estimate coming out too small on average.
≈ 35 min
The sample mean and the Central Limit Theorem
The mean of a random sample is itself a random variable. It is centred on $\mu$ , its spread shrinks like $\dfrac{\sigma}{\sqrt n}$ , and for large samples it is approximately normal whatever the population looks like.
≈ 35 min