Question

a gardener wants to determine which of two brands of fertilizer is best for the plants in a garden. before using one of the fertilizers on the entire garden, the gardener decides to conduct an experiment using 28 individual plants. which of the two plans for randomly assigning the treatments should the gardener use? explain.
plan a: choose the 14 unhealthiest - looking plants. apply brand x fertilizer to all 14 of those plants. apply brand y fertilizer to the remaining 14 plants.
plan b: choose 14 of the 28 plants at random. apply brand x fertilizer to those 14 plants and brand y fertilizer to the remaining 14 plants.
plan a, because the unhealthy plants need the fertilizer the most and should be treated first
plan b, because the sample of plants is randomly chosen
plans a and b are equivalent because they both follow experimental design
plans a and b are both poorly designed because there are not enough plants to test
the plans cannot be evaluated from the information given

Explanation:

A valid experiment to compare two fertilizers requires random assignment of treatments to plants to ensure the groups are comparable (controlling for pre-existing differences like plant health). Plan A introduces bias by selecting the unhealthiest plants for one fertilizer, which means any observed difference in growth could be due to initial health, not the fertilizer. Plan B uses random selection, creating two comparable groups, so the effect of the fertilizer can be accurately measured.

Answer:

Plan B, because the sample of plants is randomly chosen