Question

three girls won the top prize at a science fair. the girls studied the effects of treating barley seeds in different solutions before planting them. some of their findings are summarized below.

according to the information given, the manipulated variable in the experiment described is the

• time taken for the plants to germinate
• different solution treatments for the seeds
• type of potting soil used to plant the seeds
• dry mass of the plants after 37 days of growth

Explanation:

Identify the experimental setup

The text states that the girls studied the effects of treating barley seeds in different solutions before planting them. The two groups compared are:

• Water treated (control group)
• Water + bacteria treated

Define the variables

• Manipulated variable (independent variable): The factor that is intentionally changed or varied by the experimenter to test its effects. Here, this is the type of solution treatment applied to the seeds.
• Responding variables (dependent variables): The factors that are measured to see how they respond to the changes. In this experiment, these are the "time taken for the plants to germinate" and the "dry mass of the plants after 37 days of growth."
• Controlled variables: Factors kept constant, such as the type of potting soil.

Determine the correct option

The manipulated variable is the different solution treatments for the seeds.

Answer:

• time taken for the plants to germinate
• different solution treatments for the seeds (Correct answer)
• type of potting soil used to plant the seeds
• dry mass of the plants after 37 days of growth