A botanist wants to determine if a fertilizer is effective in the growth of plants. He selects the first 100 plants of the same type of seedling from a greenhouse and assigns the first 50 to the group that uses the fertilizer and remaining seedlings to the group that does not use fertilizer. He makes sure the plants all have the same amount of water, soil, and light for two months. At the end of two months, he measures the heights of the plants and finds that the ones receiving the fertilizer are significantly taller.
Answer
A
Inferences can be made for all plants, and the conclusion can be drawn that the fertilizer will help all plants grow taller.
B
Inferences cannot be made for all plants, and the conclusion can be drawn that the fertilizer will help all plants grow taller.
C
Inferences can be made for these types of plants, and the conclusion can be drawn that the fertilizer will help these types of plants grow taller.
D
Inferences cannot be made for these types of plants, and the conclusion cannot be drawn that the fertilizer will help these types of plants grow taller.
Explanation
The plants were not randomly selected or randomly assigned: the first 100 seedlings were chosen, and the first 50 received fertilizer. That makes it hard to rule out differences between the groups besides fertilizer, and the sample may not represent even all plants of the same type. So the results do not support a reliable conclusion that fertilizer caused these types of plants to grow taller.
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