Question

chloe reads that given the correct conditions, cuttings from certain plants will form roots along the stem, enabling a new plant—identical to the parent plant—to grow. chloe wants to investigate whether rooting hormone is beneficial or detrimental in this process. she takes cuttings from a shrub. for group 1, she places some shrub cuttings in potting soil in partial shade. for group 2, she dips some shrub cuttings in rooting hormone, places them in potting soil, covers them with a clear dome, and places them in direct sunlight. she waters the groups equally. she pulls up some cuttings after 3 days and again at 6 and 9 days to observe and measure root growth. all of the cuttings in group 2 died, while the cuttings in group 1 grew taller and developed roots. chloe concludes that the root hormone was harmful to the cuttings. how do you evaluate chloes experimental design? what improvement would you suggest?

Explanation:

Chloe's design has a flaw: Group 1 (no hormone, partial shade) and Group 2 (hormone, direct sun, dome) have multiple differing variables (light, dome, hormone). This means the cause of Group 2's death is unclear (could be sun/dome, not just hormone).
Suggestion: Keep all conditions (light, dome, soil, watering) identical except for the hormone. So Group 2 should also be in partial shade, no dome (same as Group 1), only differing by hormone application. This way, the effect of the hormone is isolated.

Answer:

Chloe's experiment has confounding variables (light, dome, + hormone vs. no hormone, partial shade). The death of Group 2 could be due to sun/dome, not just hormone.
Improvement: Keep all conditions (light, dome, etc.) same for both groups, only vary hormone application (e.g., Group 2: hormone, partial shade, no dome; Group 1: no hormone, same setup). This isolates the hormone's effect.