Four  key concepts are discussed in this unit:

1.Population (总体) is a collection of all possible individuals, objects, or measurements of interest.

• All the students studying business statistics
• All the registered voters in the city
• All the trees on the campus

2. Sample （样本）is a portion, or part, of the population of interest.

• The students who got A in business statistics test
• Women voters registered in the city (parts of all the people…)
• Yong trees on the campus (parts of all the trees … )

3. Parameter （参数）: A summary measure of a population is a  parameter

• A statistic computed on everyone in the population is called a population parameter.
• A property of a population. Greek letter (µ) or capital letter (P, N)

4.Statistic(统计值) – an observable property of a sample.

• Any number calculated from sample data, describes a sample characteristic.
• A statistic computed on everyone in a sample is called a sample statistic