Everything else is ready: study the parts, the key terms and the quiz below.
Random Sampling
Draw reproducible random samples and know when the sampling rule changes what the sample represents.
In this lesson6 parts
- 01Decide what the review can select
- 02Draw a simple random sample
- 03What replacement changes
- 04Guarantee coverage through declared strata
- 05A balanced review is not a population description
- 06Reproduce the selection and make the decision
Key terms
The words this lesson introduces, each in one line. The module’s glossary collects them all.
- eligible unit
- The object that can be selected once for this task; here, one invoice ID with all of its lines.
- sampling frame
- The eligible units available to draw from: 25,900 invoice IDs.
- simple random sample
- Every set of this size has equal chance.
- without replacement
- A selected unit leaves the available set.
- inclusion probability
- Chance that a specified eligible unit enters the sample: 200 / 25,900 in the simple design.
- with replacement
- Return the selected unit before the next draw; 200 such draws gave 199 distinct IDs.
- stratum
- A predeclared, nonoverlapping group used for selection; here United Kingdom, Germany, France and Other.
- stratified sample
- Separate random draws within predeclared groups.
- source-population bias
- Systematic difference between the available frame and the population a claim is meant to describe.
- weighting (narration)
- Combining strata by each stratum's share of the source frame to estimate an overall figure.
Quiz 5 questions
Your first pick on each question is the one that counts, and a right one earns a coin. Getting one wrong here is how the lesson sticks.
Practice
Problems to solve in your own notebook. Each states the problem, not the steps: working out the steps is the exercise. Level A applies the lesson, B combines it with earlier ones, C stretches it.
The self-checking notebook for this lesson is Random sampling and count models.
Common mistakes
What you will see when it goes wrong, why it happens, and the fix.
Where it’s used
Where this lesson’s ideas turn up in real work.