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.

Considering all the option:

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

(b) Age grouped as < 18, 18 - 29, 30-59, 60 > 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).

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