Task "Skier"
Student interview
male student, age 13
date of interview: 2015-04-21
In the interview the student has made a graph-as-picture error with the following explanation: Because it simply looks like the slope.
To get more information about the student's conception he has been asked when the skier is the fastest. He has answered on top and has precised by denoting the exact position with the left mark in the diagram.
So it has not entirely been clear, if the student has a wrong conception or not.
He has justified his answer as follows: Because he just comes from above and has speed there.
This argument may be based on the conception that the graph respresents the slope itself, so the student has reasoned with the shape of the slope.
On the question "Where does he slow down?" the student has drawn the second mark - in the middle - which seems to be right. But he has argumented in the following manner: He is slow because he then has to go a bit uphill.
So the student's answers seem to be (almost) right but more accurate inquiring has shown that the student interprets the graph as the slope and he reasons it with his everyday experience. So more than likely the student has a wrong conception in this case.