Answer:
Each magnet should have been tested on many different magnetizable materials
Explanation:
In designing an experiment such as that outlined above, the experimental design should have included many different magnetizable materials.
All the types of magnets; the horseshoe, the bar, and the ring magnet should have been tested using many different magnetizable materials apart from the metal object. By so doing, the strongest magnet can be effectively determined without bias because it will attract the greatest number of magnetizable materials.
Again, the shape of the magnet affects its ability to attract objects. Hence, different shapes of magnets can not effectively be compared for relative magnetic strength.
