Independent and Dependent variables worksheet - Free Printable

Let's go through each item and identify the Independent Variable (I), Dependent Variable (D), and Constants (C).

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🔹 Definitions:

- Independent Variable (I): The variable that is deliberately changed or manipulated by the experimenter.
- Dependent Variable (D): The outcome that is measured; it depends on the independent variable.
- Constants (C): Factors that are kept the same throughout the experiment to ensure a fair test.

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1. A study was done to find if different tire treads affect the braking distance of a car.

- I: Type of tire tread
- D: Braking distance
- C: Car model, speed, road conditions, driver, weight of car, brake condition

> *Explanation:* Tire tread type is what’s being changed; braking distance is what’s being measured. Other factors must be held constant.

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2. The time it takes to run a mile depends on the person’s running speed.

- I: Running speed
- D: Time to run a mile
- C: Distance (1 mile), terrain, weather, shoe type, fitness level (if controlled)

> *Explanation:* Speed is manipulated; time is measured. Distance is fixed (1 mile), so it’s a constant.

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3. The height of bean plants depends on the amount of water they receive.

- I: Amount of water
- D: Height of bean plants
- C: Type of plant, sunlight, soil type, pot size, temperature, amount of fertilizer

> *Explanation:* Water amount is varied; plant height is measured. All other growing conditions should be constant.

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4. The higher the temperature of the air in the oven, the faster a cake will bake.

- I: Oven temperature
- D: Baking time (or how fast the cake bakes)
- C: Recipe (amount of ingredients), oven type, cake size, pan material, humidity

> *Explanation:* Temperature is changed; baking time is observed. Other baking factors remain constant.

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5. Lemon trees receiving the most water produced the most lemons.

- I: Amount of water
- D: Number of lemons produced
- C: Type of lemon tree, sunlight, soil quality, fertilization, pest control

> *Explanation:* Water is varied; fruit production is measured. Other growing conditions are assumed constant.

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6. An investigation found that more bushels of potatoes were produced when the soil was fertilized more.

- I: Amount of fertilizer
- D: Bushels of potatoes produced
- C: Soil type, amount of water, sunlight, planting density, potato variety

> *Explanation:* Fertilizer amount is manipulated; yield is measured. Other farming conditions are kept consistent.

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7. Students measured the temperature of the water at different depths in Lake Skywalker and found that the temperature varied.

- I: Depth of water
- D: Water temperature
- C: Time of day, location in lake, season, water source

> *Explanation:* Depth is the variable being tested; temperature is the result. Other environmental factors are ideally constant.

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8. The amount of pollution produced by cars was measured for cars using gasoline containing different amounts of lead.

- I: Amount of lead in gasoline
- D: Amount of pollution produced
- C: Car model, engine type, driving conditions, speed, fuel efficiency, mileage

> *Explanation:* Lead content in fuel is changed; pollution output is measured. Cars and driving conditions are controlled.

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9. Four groups of rats are first massed and then fed identical diets except for the amount of vitamin A they receive. Each group gets a different amount. After 3 weeks on the diet, the rats’ masses are measured again to see if there has been a decrease.

- I: Amount of vitamin A in diet
- D: Change in mass (or final mass of rats)
- C: Diet (except vitamin A), initial mass, environment, cage conditions, water intake, age of rats, duration of experiment

> *Explanation:* Vitamin A amount is varied; change in body mass is measured. All other aspects of care are identical.

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✔ Final Answers:

| # | I (Independent) | D (Dependent) | C (Constants) |
|---|-------------------------------|----------------------------------|----------------|
| 1 | Type of tire tread | Braking distance | Car model, speed, road conditions, etc. |
| 2 | Running speed | Time to run a mile | Distance, terrain, weather, etc. |
| 3 | Amount of water | Height of bean plants | Sunlight, soil, pot size, etc. |
| 4 | Oven temperature | Baking time | Recipe, cake size, pan, etc. |
| 5 | Amount of water | Number of lemons produced | Tree type, sunlight, soil, etc. |
| 6 | Amount of fertilizer | Bushels of potatoes produced | Soil, water, sunlight, etc. |
| 7 | Depth of water | Water temperature | Time of day, location, season, etc. |
| 8 | Amount of lead in gasoline | Amount of pollution produced | Car model, driving conditions, etc. |
| 9 | Amount of vitamin A | Change in rat mass | Diet (other than vitamin A), environment, etc. |

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