Brainlag PlusSampling and populations
Choose a random sample, spot bias, use a sample to estimate counts, means and totals for a whole population, judge which sample is more reliable, and (Higher) estimate a population by capture-recapture.
Population, sample and bias
The population is everyone (or everything) you want to know about. A sample is the part you actually ask or measure. In a random sample every member of the population has the same chance of being chosen: number them all and pick with a random number generator.
A sample is biased when the way it is chosen makes some answers more likely than they are in the population. Asking people leaving a gym how much they exercise, or the first people to reply online, gives a biased sample. A bigger sample is more reliable, but only if it is random: a big biased sample is still biased.
The rest of this lesson and its 10 practice questions are in Plus.
Screen 1 of 4, free to read.
- 10 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards