sampling clt · Lesson 1 of 7
Population vs Sample
Population
A population is the entire group of individuals or items that you want to study. Population values are called parameters and are typically denoted by Greek letters (μ, σ, p).
Sample
A sample is a subset of the population actually observed. Sample values are called statistics and are denoted by Latin letters (x̄, s, p̂).
Why Sample?
Studying an entire population is usually too expensive, time-consuming, or impossible. A well-chosen sample lets us make reliable inferences about the population at a fraction of the cost.
Example
Population: all 10,000 students at a university. Sample: 200 randomly selected students. If the sample mean GPA is 3.2, we use that to estimate the population mean GPA.