Question

rajesh designed an experiment to test the effect of fertilizer on plant growth. the table on the right shows the data he collected. which changes should rajesh make to his experiment to improve the validity of the data? check all that apply.

• add twice as much fertilizer to the plants.
• measure the growth of a plant that did not receive fertilizer.
• perform additional trials.
• remove plant 2.

Explanation:

Analyze the current experimental setup

The experiment tests the effect of fertilizer on plant growth. The table shows three plants, each receiving a different amount of fertilizer (\(2.0\text{ mL}\), \(3.0\text{ mL}\), and \(4.0\text{ mL}\)), with only one trial per treatment. There is no control group (a plant receiving \(0\text{ mL}\) of fertilizer) to establish a baseline for growth without fertilizer.

Evaluate the first option

"Add twice as much fertilizer to the plants."
Increasing the dosage does not address the lack of a control group or the small sample size. It does not improve the validity of the data.

Evaluate the second option

"Measure the growth of a plant that did not receive fertilizer."
Using a control group is a fundamental concept in Precision and Accuracy and experimental design. It establishes a baseline to prove that the growth is actually caused by the fertilizer.

Evaluate the third option

"Perform additional trials."
Having only one plant per treatment level makes the data susceptible to individual variations. Performing multiple trials (replication) increases reliability and data validity.

Evaluate the fourth option

"Remove plant 2."
Removing data points without justification reduces the sample size further and decreases the validity of the experiment.

Answer:

• Add twice as much fertilizer to the plants.
• Measure the growth of a plant that did not receive fertilizer. (Correct answer)
• Perform additional trials. (Correct answer)
• Remove plant 2.