Collecting Data and Sampling
From population to sample
Why sampling matters
A population is often too large to measure completely, so statisticians study a sample and use it to learn about the population.
Common sampling methods
Be careful with bias
A sample can be misleading if it overrepresents some groups and misses others.
A simple sampling workflow
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Step 1: Define the population clearly.
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Step 2: Decide what variable you want to measure.
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Step 3: Choose a sampling method.
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Step 4: Collect the data carefully.
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Step 5: Check for missing or suspicious values.
Which sampling method is generally best for reducing bias?
Random sampling gives each member a known chance of selection and helps reduce bias.
Correct answer: Random sample
What is a population in statistics?
A population includes all individuals or items relevant to the question.
Correct answer: The entire group being studied.
Which sample is most likely to be biased?
Volunteer samples can overrepresent people who choose to respond.
Correct answer: A sample of people who volunteer online
Why can convenience samples be a problem?
Convenience sampling often introduces bias because the easiest people to reach are not always typical.
Correct answer: They may not represent the whole population well.