Twenty families were asked how many story books they bought last month. The replies were 2, 0, 3, 1, 2, 4, 1, 0, 2, 3, 5, 2, 1, 3, 2, 0, 4, 2, 1, 3. After making a frequency table, how many families bought fewer than 3 books?

Tallying the replies gives 0 books: 3 families, 1 book: 4, 2 books: 6, 3 books: 4, 4 books: 2, 5 books: 1 — twenty in all. 'Fewer than 3' covers 0, 1 and 2 books: 3 + 4 + 6 = 13 families. Including the 4 families who bought exactly 3 would give 17, while 7 counts those who bought 3 or more.