Ready to differentiate between e.g. and i.e.?
A memory trick: Think of “egg·sample” (get it?) as a reminder that e.g. introduces an example.
In an intriguingly titled piece called “Communication with Aliens,” John Durham Peters1 correctly uses e.g. in his paraphrase of a study on self-described psychics done by researcher Ian Hacking2
Investigation into telepathy was the origin of randomized design; the experimenter could thus be completely blind to any order created (e.g., in the arrangement of playing cards) so as to bar any unwitting collaboration from his or her unconscious.
Speaking into the Air: A History of Communication
Use i.e. when you need to rephrase or explain the word(s) that came immediately in front of it. A memory trick: i.e. and “is” are both two letters and each begins with an “i.”
James Trefil, author of A Scientist in the City, uses i.e. correctly to explain what he means by “productive”:
Trafalgar Square in London and the Piazza San Marco in Venice … can be covered almost solidly with pigeons at times. The weight of the living pigeons is probably greater than the total weight of living animals on any comparably sized wild habitat. Urban ecologists … argue that the ecosystems they study are more “productive” (i.e., produce more animal biomass) than any others (10).3
Neither i.e. or e.g. gets written in italics.
1 Peters, John Durham. Speaking into the Air: A History of Communication. Chicago: University of Chicago Press, 1999.
2 Hacking, Ian. “Telepathy: Origins of Randomization in Experimental Design.” Isis 79 (1988) 427-51.
3 Trefil, James. A Scientist in the City. New York: Doubleday, 1994.