Keep in mind that even if you state the facts you are relying on for your opinion, but those facts turn out to be false, the privilege will not apply. For example, if you say that "In my opinion, Danielle is failing out of school because she failed biology," the privilege would not apply if she got a C in biology.
To determine whether a statement is an opinion or a fact, courts will generally look at the totality of the circumstances surrounding the statement and its publication to determine how a reasonable person would view the statement. Under this test, the difference between an opinion and a fact often comes down to a case-by-case analysis of the publication's context.
Distinguishing Between Statements of Fact and Opinion
In general, facts are statements that can be proven true or false; by contrast, opinions are matters of belief or ideas that cannot be proven one way or the other. For example, "Chris is a thief" can be proven false by showing that throughout his entire life Chris never stole anything. Compare that statement with "Chris is a complete moron." The latter is an opinion (or, technically, "a pure opinion"), as what constitutes a moron is a subjective view that varies with the person: one person's moron is not necessarily the next person's moron. Put another way, there would be no way to prove that Chris is not a moron. If a statement is a "pure opinion," it cannot be the basis for a defamation claim.