Science: Interpreting a Seed-Germination Investigation
A student places 30 bean seeds in each of three trays. Tray 1 is kept at 10 degrees Celsius, Tray 2 at 20 degrees Celsius, and Tray 3 at 30 degrees Celsius. All trays receive the same amount of water and light. After ten days, germination counts are 6, 21, and 24 seeds. On day eight, the student notices mold in Tray 3 and removes the affected seeds, but includes the tray in the final count. The student concludes that 30 degrees Celsius is the best temperature for germination and that temperature alone determines germination.
1. Identify two flaws or limitations in the investigation and explain how each affects the conclusion.
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First, mold appeared in Tray 3 and affected seeds were removed, so the 24 count may be distorted and the tray experienced a condition the others did not. This weakens any claim that 30 degrees is superior, because the result may reflect contamination or handling rather than temperature. Second, the experiment tested only three temperatures with no replicates, so a single tray per temperature cannot separate temperature effects from chance variation among trays. Third, concluding that temperature alone determines germination ignores that water, light, and seed quality were controlled but not varied, so their necessity was never tested.
2. The student wants to strengthen the claim. Describe a revised design and state what result would support the conclusion.
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A stronger design would use several trays per temperature, for example three trays of 30 seeds at each of 10, 20, and 30 degrees, with identical water, light, and seed source, and would monitor and report mold consistently across all trays. Germination should be counted on the same schedule, and contaminated seeds should be handled by the same rule in every tray.
The conclusion would be supported if replicated trays at 30 degrees consistently show the highest germination percentage and the differences are larger than the variation among trays at the same temperature. Even then, the claim should be limited to the temperatures tested and to bean seeds under these conditions, not to germination in general.