Final answer:
The incorrect sentence is 'c. The XYZ consumer doesn't want to look her age' because it refers to an attitude rather than a demographic variable.
Step-by-step explanation:
The sentence that references a variable that isn't demographic in describing the XYZ Company's primary customer group is: c. The XYZ consumer doesn't want to look her age. This sentence refers to an attitude or a desire, rather than an objective demographic variable such as age, income, family size, or marital status. In contrast, sentences a, b, and d mention quantifiable demographic variables, including the customer's age, income level, and family status.