Sample A
Two sets of data vary directly if the value of y divided by x is that same for all corresponding data.  A graph of direct variation always goes through (0,0).

Sample B
If the ratio of each value in one set to its matching value in the other set is the same then the data vary directly.  A line is the graph of a direct variation if the ratios of x and y are equal.

Teacher Comments
This exit slip was designed to get students to think critically about the concept of direct variation.  Both answers demonstrated understanding of how to determine whether direct variation is represented.  Sample  A demonstrates that the student has noticed graphs of direct variations always pass through the origin, while example B paraphrases the process practiced in class.