Scientific Method Practice Answer Key - Fill Online, Printable ... - Free Printable

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PROBLEM 1:

Scenario Summary:
Mary is testing whether different concentrations of Miracle-Grow affect plant growth. She uses three groups of tomato plants (each with 30 plants):

- Group A: 5% Miracle-Grow
- Group B: 10% Miracle-Grow
- Group C: 20% Miracle-Grow

All plants are watered daily and kept under identical conditions (light, temperature, etc.). After 30 days, she measures plant height.

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PART 1: EXPERIMENTAL TERMS

Let’s define each term in the context of this experiment.

#### 1. Independent variable:
The independent variable is the factor that the experimenter deliberately changes.

> ✔ Answer: The concentration of Miracle-Grow (5%, 10%, or 20%).

This is what Mary is changing between the groups.

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#### 2. Dependent variable:
The dependent variable is what is measured or observed as a result of the change in the independent variable.

> ✔ Answer: The height of the plants after 30 days.

This is what Mary is measuring to see if Miracle-Grow affects growth.

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#### 3. Controlled variables:
These are factors that are kept constant so they don’t influence the results.

> ✔ Answer: Amount of sunlight, amount of water each day, type of soil, temperature, container size, etc.

(Any factor that is the same across all groups.)

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#### 4. Control group:
The control group is the group that does not receive the experimental treatment. It serves as a baseline for comparison.

> ✔ Answer: There is no true control group in this setup because all groups receive Miracle-Grow. However, if we had a group with 0% Miracle-Grow (just water), that would be the control.

But since all groups have Miracle-Grow, none is a true control. So:

> ✘ This experiment lacks a control group unless one was included without Miracle-Grow.

If we assume that Group A (5%) is the lowest concentration and used as reference, it might be considered a baseline, but not a true control.

So, strictly speaking:
> ✔ Answer: There is no control group in this experiment as described.

But if the question expects a choice among the groups, then none qualifies as a true control.

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Questions:

#### 1. In this scenario, what is the independent variable?

> ✔ Answer: The concentration of Miracle-Grow (5%, 10%, or 20%).

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#### 2. What is the dependent variable?

> ✔ Answer: The height of the plants after 30 days.

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#### 3. In this scenario, what are the controlled variables? (Identify at least three)

> ✔ Answer:
> - Amount of water given each day
> - Amount of sunlight
> - Type of soil
> - Temperature
> - Size of pots
> - Plant species and initial size (assuming all started the same)

*(Any three of these are acceptable.)*

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#### 4. Which group would be the control group in this experiment?

> ✔ Answer: There is no control group in this experiment because all groups received Miracle-Grow. A proper control group would be a group receiving no Miracle-Grow (e.g., only water). Since that group is missing, there is no control.

> ⚠️ If the question assumes one of the groups is a control, then none of them are truly controls. But if you must pick one, Group A (5%) might be considered the lowest dose, but still not a true control.

> ✔ Best Answer: There is no control group.

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✔ Final Answers:

1. Independent variable: Concentration of Miracle-Grow
2. Dependent variable: Height of the plants
3. Controlled variables: Water amount, sunlight, temperature, soil type, pot size, etc.
4. Control group: None (no group receives no Miracle-Grow; thus, no true control)

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