Pepper Plants

Conclusions and Reflections

Pepper Plants began the TIMSS 2019 PSI task development process, and had the longest evolution and the most revisions. As an exercise in experimental design and interpretation in a biological context, great effort was expended in developing a scenario that was as realistic as possible (albeit a simulated situation) and that provided students with interesting and engaging activities in designing and setting up their experiment.

• Pepper Plants seems to have hit the right note in terms of student engagement and item difficulty, with very few students not managing to complete the task in the time allowed.
   
• Experience from the TIMSS field test confirmed that the activities involved in designing and setting up the experiment, such as deciding which fertilizer to apply and in what amount, and how much water to supply, were engaging and motivating for the students.
   
• However, the field test also showed that a well-balanced task would, in addition, require emphasis on students’ reasons for their design choices, their understanding of the characteristics of good design, and their ability to interpret and make generalizations from the results. The final version included items addressing these issues.
   
• The Pepper Plants task shows that experimental setup and design can be a fruitful area for future Problem Solving and Inquiry tasks. The results indicate that eighth grade students have a reasonable grasp of the idea of an experiment as a fair test, but less understanding of an effective experimental control.