A book publisher publishes both fiction and nonfiction books. Let F represent the number of words, per chapter, for fiction books, and let N represent the number of words, per chapter, for nonfiction books. The standard deviation of the total amount, S = F + N, is 195.3 words. What is the interpretation of this value?

The mean number of words per chapter will vary from book to book.
On average, there are 195.3 words total in a typical chapter of either genre of book.
This publisher can expect the total number of words per chapter to vary by approximately 195.3 words from the mean.
If we combine the fiction and nonfiction books from this publisher, the average number of words per chapter will change by 195.3.