My sister can run faster than I. This is the grammatically correct form –than I, as traditionalists frequently point out, is short for than I can. However, the form that is considered correct by traditionalists sometimes sounds rather pedantic in speech: My sister can run faster than I can is correct, but My sister can run faster than me is more frequently used. Filling in the missing verb is often a good way of preserving grammar and avoiding awkwardness: She spent far less time on it than he did