In which scenario would one primarily use nominal data?

Nominal data is used to categorize information without a meaningful order or ranking. It allows for the classification of variables into distinct categories based on qualitative attributes. In this context, categorizing pets by type is a prime example of nominal data usage. Pets can be classified into different categories such as dogs, cats, birds, and reptiles. Each type of pet represents a unique category that does not have an inherent rank or order; they are simply different types of entities.

In contrast, ranking levels of education would involve ordinal data, as education levels can be ordered based on attainment. Measuring temperature typically involves interval or ratio data, where numerical values indicate differences in magnitude. Defining income levels may also suggest an ordinal relationship, as income can be categorized into ranges but these ranges imply an order. Therefore, the scenario of categorizing pets clearly is aligned with the characteristics of nominal data, making it the most appropriate choice.