The research question are examined in more detail by means of a qualitative hypothesis generating case study. Therefore the GeoGebra applets are used in a 7th grade of a middle school in Austria. The qualitative analysis is carried out using methods of Grounded Theory (Glaser & Strauss, 1998).
The data collection is divided into a process that involves five stages.

Data collection

Stage 1: Diagnostic test 1

Contains tasks concerning different pre- and misconceptions;

Then students are divided into 2 groups;

Stage 2: Diagnostic interviews

Concerning tasks from diagnostic test 1;

With 8 students of group 2;

Stage 3: Intervention

Use of GeoGebra applets in class;

Students working independently in pairs;

Duration: 3 lessons;

Recording (audio, video, screen) of students of group 1;

Stage 4: Diagnostic test 2

Contains tasks concerning conceptions slightly different from diagnostic test 1;

With all students;

Stage 5: Diagnostic interviews

Based on analysis of recordings and diagnostic test 2;

With 8 students of group 1;

If necessary interviews with teachers about the design of the applets will be conducted.

Diagnostic test 1

Here are some tasks of the diagnostic test 1. The first two tasks (Area, Skier) are according to examples from Schlöglhofer (2000). The third one is from a german test instrument called CODI, which has been designed by Nitsch (2015) to diagnose misconceptions concerning functional relationships.

Task "Skier"

You see a skier who is descending a slope. The graph shows the speed of the skier in the course of time. Which of these 4 diagrams is describing the situation best?

Task "Area"

Here a trapezoid is displayed. Imagine you draw the dotted line from vertex A to the right by the distance x. In doing so you observe the changes in the size of the grey marked area.

In the diagram the grey-shaded area is a function of distance x. Which of these 4 diagrams is correct?

Task "Car"

Which of the 4 cars is the fastest at the time t = 5 seconds?