The representational differences were first examined across the 12 open-ended assessment tasks (see Cai, 2000,
for a complete list of these 12 tasks). To examine the representational differences across the 12 tasks, each student
was assigned a representational score. To assign a representational score to a student, the total number of questions
was first determined. Some problems contain only one question each (e.g., Hats Averaging, Number Theory), whereas
other problems contain more than one question (e.g., Block Pattern has two questions — How many blocks are needed
to build a staircase of 5 steps? How many blocks are needed to build a staircase of 20 steps?). There are a total of 19
questions across the 12 problems. The number of times a student used a representation to answer these questions was
then determined. For example, a student might have used symbolic representations on 5 of the 19 questions, pictorial
representations on 6 of the 19 questions, and verbal representations on 4 of the 19 questions. For the remaining
questions, the student might not have provided any written record of using a representation. A student’s representation
score was determined based on the ratio of the number of times a particular representation was used to the total number
of questions (i.e., 19). For example, for the above student, his/her representation scores would be 5/19 for symbolic,
6/19 for pictorial, and 4/19 for verbal