The answer to the first free response part c I believe is incorrect.  The answerer describes friction (air resistance) as being upwards.  This I believe is incorrect since the marble was launched upwards and air resistance should therefore be downwards.  This changes the answer from "bigger" to "smaller".  The answer of smaller also corresponds to the concept that without air resistance, the graph would have a more shallow slope (assuming v^2 on the y axis and h on the x-axis).  A more shallow slope corresponds to a smaller acceleration.

Michael, thank you for your detailed correction, and you are right.  This is what I replaced the existing answer with, please let me know if that works.  Thanks, John

Smaller. The calculated value assumed no friction and the acceleration was due totally to the gravitational acceleration. But the data also included a downward acceleration, af, due to friction. The calculated g from the slope of the line was equal to g + af. Therefore, the real value of g is less than the calculated value