Final answer:
The data set of book titles read by a student, including 'Spring Fever,' 'Private London,' and others, represents a nominal level of measurement, used for categorizing data without implying any order or rank.
Step-by-step explanation:
The list of books that your friend read for school for the past five months includes titles such as Spring Fever, Private London, The Racketeer, The Forgotten, and Threat Vector. This data set represents a nominal level of measurement. In statistics, the nominal level of measurement is used to categorize data without a natural order or ranking among the categories. Book titles fall into this category as they are labels that enable us to discern one book from another but do not imply any relative positioning or order of the books in terms of value, importance, or quantity.
With nominal data, we can count how many times each book title appears if there are duplicates, or we can determine the mode, which is the book title that appears most frequently. However, we cannot perform any arithmetic operations on the titles, such as taking an average, because they do not have a numerical value associated with them. Hence, the data set of book titles is purely qualitative, and its purpose is for classification and identification only.