Which of the following variables is Nominal? Select one: a. Age (in years) b. Age (grouped as: less than 18, 18-29, 30-59, 60 and older) c. Car color (e. g. red, blue, grey) d. Letter grade in a course (e. g. A+, A, A-, B+, B)

c. Car color (e. g. red, blue, grey)

Step-by-step explanation:

There are four level of measurements: Ordinal, Nominal, Interval and Ratio.

Ordinal variables are categorical variables and have a ordered categories. For example, the health of patients: Excellent, Good, Average and Poor. Nominal variables are also categorical variables but they do not have a ordered category or any numerical value. For example, Gender: Male or Female, or Occupation:, Accountant, Clerk, Manager. Interval variable are variables that take numerical values. These variables are ordered and the difference between two values is meaningful. For example, temperature in degrees F. Ratio variable are type of interval variables but they do not have a variables with a 0 measurement. For example, height, age, money.

Considering all the option:

(a) Age (in years) is an interval variable.

(b) Age grouped as are basically ordered categorical variables. Thus, they are ordinal variables.

(c) Car Color (red, blue, grey) are nominal variable because they are not ordered and cannot be measured.

(d) Letter grade in a course (A+, A, A-, B+, B) are also ordinal variables because they are ordered and represent the performance quality of the student.

Thus, the correct answer is (c).