The following data show the number of times different students of a class practice swimming in a month:

3, 5, 7, 3, 4, 4, 2, 1, 3, 5, 2, 3, 7, 2, 3, 4, 1, 2, 4

The dot plot below was made to represent the data.

A box plot showing 3 dots over 1, 4 dots over 2, 5 dots over 3, 4 dots over 4, 2 dots over 5, no dot over 6, and 2 dots over 7

For which number is the data plotted incorrectly?

1
3
4
5