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Difficulty: EasyIdentifying Independent, Dependent, and Controlled Variables

A student designs an experiment to compare the sound-dampening ability of various insulation materials. Four identical wooden boxes are lined with a 2 cm2\text{ cm} layer of a different material: fiberglass, acoustic foam, cellulose, or mass-loaded vinyl. A sound generator inside each box plays a tone at a fixed intensity of 85 dB85\text{ dB}. A decibel meter placed 1 m1\text{ m} outside the box measures the remaining sound intensity. In this experiment, which of the following is the dependent variable?

  1. A
    The type of insulation material used to line the wooden box
  2. The sound intensity measured by the decibel meter outside the boxAnswer
  3. C
    The thickness of the insulation material layer (2 cm2\text{ cm})
  4. D
    The initial intensity of the sound played inside the box (85 dB85\text{ dB})

Answer

The dependent variable is the sound intensity measured by the decibel meter outside the box.
The sound intensity measured by the decibel meter outside the box is the dependent variable because it is the outcome observed and measured to evaluate the effectiveness of each insulation material.

Step-by-Step Solution

1
Identify the factor intentionally changed by the experimenter (Independent Variable).
The insulation material type (fiberglass, foam, cellulose, vinyl) is varied systematically.
The independent variable is the condition tested or manipulated.
2
Identify the factor being measured as an outcome (Dependent Variable).
The remaining sound intensity output measured by the decibel meter outside the box.
The dependent variable responds to changes made to the independent variable.
3
Identify the factors kept constant across all trials (Controlled Variables).
Material thickness (2 cm2\text{ cm}), initial tone volume (85 dB85\text{ dB}), box structure, and distance to the decibel meter (1 m1\text{ m}).
Controlled variables ensure that observed changes in the dependent variable are due solely to the independent variable.

Key Concept

Identifying Independent, Dependent, and Controlled Variables
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Topics

Identifying Independent, Dependent, and Controlled Variables

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