This worksheet guides students through a science experiment scenario involving lima bean plants and aged compost to practice identifying key experimental variables.

Let's carefully analyze the scenario and fill in the Experimental Design Diagram step by step. This is a classic scientific experiment setup, and we need to identify the key components: problem, hypothesis, variables, groups, and constants.

---

🔍 Scenario Summary

- Goal: Investigate how different aged grass compost affects lima bean plant growth.
- Hypothesis: Older compost produces taller plants.
- Setup:
- 3 trays of 25 plants each → total 75 plants.
- Each tray has 450 grams of soil mix.
- Tray 1: ½ potting soil + ½ 3-month-old compost
- Tray 2: ½ potting soil + ½ 6-month-old compost
- Tray 3: Only plain potting soil (no compost)
- All plants get:
- Same amount of sunlight
- Same amount of water
- Kept in same location
- Measured: Plant height in cm after 30 days

---

Now let’s complete the Experimental Design Diagram:

---

✔ Completed Experimental Design Diagram

| Problem: | What effect does the age of grass compost have on the growth of lima bean plants? |
|--------------|-----------------------------------------------------------------------------|
| Hypothesis: | Older compost will produce taller lima bean plants. |
| Independent Variable: | Age of the compost used in the soil mixture |
| Groups to be Tested Description | Tray 1: 3-month-old compost mixed with potting soil<br>Tray 2: 6-month-old compost mixed with potting soil<br>Tray 3: Plain potting soil (no compost) |
| Number to be Tested in Each | 25 plants per tray |
| Dependent Variable | Height of the lima bean plants (in centimeters) after 30 days |
| Constant Variables | Amount of soil (450 grams), amount of sunlight, amount of water, location, type of plant (lima beans), duration of experiment (30 days), planting conditions |

---

📌 Explanation of Each Part

1. Problem:
The question being investigated — what are they trying to find out?
→ They want to know how compost age affects plant growth.

2. Hypothesis:
A prediction based on prior knowledge.
→ "Older compost will produce taller plants" is directly stated.

3. Independent Variable:
The factor that is deliberately changed.
→ The age of the compost (3 months vs. 6 months vs. none).

4. Groups to be Tested:
The three experimental conditions (treatments).
- Tray 1: Young compost (3 months)
- Tray 2: Older compost (6 months)
- Tray 3: Control group (no compost)

5. Number to be Tested in Each:
→ 25 plants per tray (replication for reliability).

6. Dependent Variable:
What is being measured or observed.
→ Plant height in centimeters after 30 days.

7. Constant Variables:
Everything kept the same across all groups to ensure a fair test.
→ Soil amount, watering, sunlight, location, plant type, time period, etc.

---

✔ Final Notes:

This is a well-designed controlled experiment because:
- Only one variable (compost age) is changed.
- All other factors are held constant.
- There is a control group (plain soil).
- Replication (25 plants per group) increases reliability.

This helps isolate the effect of compost age on plant growth.

---

Let me know if you'd like this formatted as a printable worksheet!