When designing research, variables may be specified three ways:
1. DEPENDENT VARIABLE, operationalized two ways:
Continuous variable "DV"
Example: Body Mass Index, computed as weight in kilograms divided by the square of height in meters, and possibly ranging from 8 to 55
Categorical variable [with only 2 categories, "DV-0" and "DV-1", where "DV-1" is the most important category].
Example: Whether or not a student is overweight.
The variable Overweight could be coded:
0 = BMI less than 25
1 = BMI greater than or equal to 25
HINT: Never categorize a variable based on its average (mean).. INDEPENDENT VARIABLE, operationalized two ways:
Continuous variable "IV"
Example: Number of hours that a student watches television on a typical school night. This ranges from no hours (0) to many hours.
Categorical variable [with only 2 categories, "IV-0" and "IV-1", where "IV-1" is the most important category].
Example: Whether or not a student watches four or more hours of television on a typical school night. The number of TV hours could be coded:
0 = No television or less than 4 hours
1 = Watches 4 or more hours of television.
3. Other independent variables, known as
CONTROL VARIABLES "C" [don't worry about continuous versus categorical]
Examples: Sex (Male, Female) and Age.
Other control variables include, for example, the number of calories consumed per day, number of days per week that the student does aerobic exercise for 20 or more minutes, and number of days per week that the student uses weights to tone muscles.