Study design and flow of participants. All students that responded to the study invitation were randomised and could participate in the ECG session. The ECG session consisted of a pre-test, the ECG tutorial and a post-test. The participants also completed a retention-test after either short, medium or long follow-up as determined by randomisation. The only difference between the three follow-up groups was the length of the follow-up interval. The number of participants in each step of the study is indicated in the right side of the figure.