(1) In the rubric, the third 1-point entry says that 3/2 with no work does not get the point. What is "appropriate work"?
Answer: (4-1)/(4-2) = 3/2, or change in y/change in x = 3/2, or a sketch on a grid. But no, just 3/2 with no work does not earn the point.
(2) In that case, for full credit, can they just write 3/2 and then have -2/3 as a final answer, or do they need to show work for how they found 3/2?
Answer: It is full credit if student just writes 3/2 followed by -2/3.
(3) Isn't that inconsistent?
Answer: Yes, but it's a two-point question, you can't make fine distinctions.
(4) If, despite our best efforts to make sure students know the scrap graph paper will not be graded, a student writes "see work on graph paper," can we look at the graph paper for work? No, the graph paper may not be scored.
(5) We feel that the question should have had a grid, with "use of the grid is optional."
Answer: they were probably trying to force an algebraic response.
Our reply: We feel this was an awkward way to do that, since it's not clear to the student what work is needed. Maybe a better way to do that is to ask for the slope from (1, 2) to (5, 75).