1.1 - Cases & Variables

When conducting a research study, information is collected concerning cases. Cases are also sometimes known as units or experimental units.

variable is a characteristic that is measured and can take on different values. In other words, something that can vary. This is in contrast to a constant which is the same for all cases in a study.

Case
An experimental unit from which data are collected
Variable
Characteristic of cases that can take on different values (in other words, something that can vary)

Example: STAT 200 Student Data Section

Data are collected from a sample of STAT 200 students. Each student's Lesson 1 quiz, lab assignment, and homework score is recorded. In this example, the cases are the students. The variables are the Lesson 1 quiz, lab assignment, and homework scores.

Example: Relationship between Homework & Exam Grades Section

A third grade teacher wants to know if students who spend more time studying at home get higher homework and exam grades. In this example, the third grade students are the cases. The variables are the homework and exam grades.

Example: Dog Food Study Section

A researcher wants to know if dogs who are fed only canned food and only hard food have different body mass indexes (BMI). They collect BMI data from 50 dogs who eat only canned food and 50 dogs who eat only hard food. Here, the cases are the dogs. The variables are a type of dog food and BMI.