Do students understand that there are many weight values (possible weights) between any two numbers, for example, between 3 and 4?
By listening to their discussion, you can find evidence of students' understanding of what their measurement readings do and don't tell them. In the following classroom, students have found that one cube was heavier than another but measured in bears, their weights are the same (2 bears).
As she interprets students' ideas, Jen listens for the idea that a cube is unlikely to weigh exactly a whole number of bears. One cube may weigh between 2 and 3 bears but closer to 2, and another cube between 1 and 2 bears but closer to 2. Thus the two cubes weigh the same number of whole bears and yet one cube actually weighs a little more than the other.
As a next step, the teacher in this class encouraged students to suggest other explanations.