Technical Mathematics, Sixth Edition

21.1. Definitions and Terminology

21.1.1. Populations and Samples

In statistics, an entire group of people or things is called a population or universe. A population can be infinite or finite. A small part of the entire group chosen for study is called a sample.

Example 1: In a study of the heights of students at Tech College, the entire student body is our population. This is a finite population. Instead of studying every student in the population, we may choose to work with a sample of only 100 students.

Example 2: Suppose that we want to determine what percentage of tosses of a coin will be heads. Then all possible tosses of the coin are an example of an infinite population. Theoretically, there is no limit to the number of tosses that can be made.

21.1.2. Parameters and Statistics

We often use just a few numbers to describe an entire population. Such numbers are called parameters. The branch of statistics in which we use parameters to describe a population is referred to as descriptive statistics.

Example 3: For the population of all students at Tech College, a computer read the height of each student and computed the average height of all students. It found this parameter, average height, to be 68.2 in.

Similarly, we use just a few numbers to describe a sample. Such numbers are called statistics. When we then use these sample statistics to infer things about the entire population, we are engaging in what is called inductive statistics.

Example 4: From the population ...