lesson
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If a chef wants to check if a giant 10-gallon pot of soup needs more salt, they don't drink the whole pot. They stir it thoroughly and taste a single spoonful.
In statistics, the entire group you want to learn about is called the population, while the smaller part you actually inspect is the sample.
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How you choose that sample determines whether your survey reflects reality or gives you totally misleading numbers.
Simple Random Sampling
In simple random sampling, every single member of the population has an exact, equal chance of being chosen.
You can think of this like placing every student's name into a giant bingo cage, spinning it, and drawing out 30 names at random.
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Random drawings prevent human favoritism, but what if you have an ordered list of thousands of people and want an easy, regular rule to follow?
Systematic Sampling
In systematic sampling, you pick a random starting point on a list and then select every k-th individual at regular intervals.
To find your interval step k, you divide your total population size N by your desired sample size n using the formula k=nN.
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