EXAMPLE 1.3
Statistics class data. Suppose that you are a teaching assistant for a statistics class and one of your jobs is to keep track of the grades for students in two sections of the course. The cases are the students in the class. There are weekly homework assignments, two exams during the semester, and a final exam. Each of these components is given a numerical score, and the components are added to get a total score that can range from 0 to 1000. Cutoffs of 900, 800, 700, etc., are used to assign letter grades of A, B, C, etc.
The spreadsheet for this course will have seven variables:
An identifier for each student.
The number of points earned for homework.
The number of points earned for the first exam.
The number of points earned for the second exam.
The number of points earned for the final exam.
The total number of points earned.
The letter grade earned.
The student identifier is a label and the letter grade earned is a categorical variable. All the other variables are measured in “points.” Because we can do arithmetic with their values, these variables are quantitative variables.