Let us organize important terms used in sample surveys.
- Population: The entire group to be studied
- Sample: A part taken from the population
- Sample size: The number of items taken
- Random sampling: A method of selecting a sample randomly, without bias
📘 Example ①
A random sample of 100 people was selected from 3000 people in a city to investigate an approval rating. State the population, sample, and sample size.
Answer:Population = all 3000 people in the city. Sample = the 100 people selected. Sample size = 100.
A random sample of 100 people was selected from 3000 people in a city to investigate an approval rating. State the population, sample, and sample size.
Answer:Population = all 3000 people in the city. Sample = the 100 people selected. Sample size = 100.
💡 Key Point
- Random sampling: Ensure that everyone has the same probability of being selected
- If the sample is biased, an accurate estimate cannot be made
Practice Problem
- Fifty products were taken from 2000 products and inspected. State the population and sample size.
Answer and Explanation
- Answer:Population = all 2000 products. Sample size = 50.