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Zorluk: OrtaIdentifying Sources of Error and Confounding Variables

A student investigates how different colors of light affect the rate of photosynthesis in *Elodea* plants. The student places one *Elodea* plant in each of four separate glass beakers filled with water. Each beaker is exposed to a different color of light (red, blue, green, or white) by placing colored filters over the light source. To ensure enough light reaches each beaker, the student places the beakers at different distances from the light source: the beaker with the green filter is placed 10 cm10\text{ cm} away, the blue filter beaker is 20 cm20\text{ cm} away, the red filter beaker is 30 cm30\text{ cm} away, and the white light beaker is 40 cm40\text{ cm} away. After two hours, the student measures the volume of oxygen gas produced by each plant. Which of the following identifies a confounding variable in this experimental design that invalidates the student's conclusion about the effect of light color?

  1. A
    The volume of oxygen gas produced, because it varies depending on the color of light.
  2. B
    The species of plant used, because different plant species have different baseline rates of photosynthesis.
  3. The varying distances of the beakers from the light source, which changes the light intensity received by each plant.Cevap
  4. D
    The duration of light exposure, because two hours may not be long enough to observe a measurable difference.

Cevap

The varying distances of the beakers from the light source, which changes the light intensity received by each plant.
The correct answer is the option stating that the varying distances of the beakers from the light source is a confounding variable. Changing the distance of the plant from the light source alters the light intensity it receives. Because both the color of light and the light intensity vary among the beakers, it is impossible to determine which factor caused any observed changes in the volume of oxygen gas produced.

Adım Adım Çözüm

1
Identify the independent variable (the variable intended to be changed) and the dependent variable (the variable being measured).
The independent variable is the color of light (red, blue, green, white). The dependent variable is the volume of oxygen gas produced.
This establishes the relationship that the experiment is designed to test.
2
Scan the experimental setup to identify any other variables that changed between the different treatment groups.
The student placed the beakers at different distances (10 cm10\text{ cm}, 20 cm20\text{ cm}, 30 cm30\text{ cm}, and 40 cm40\text{ cm}) from the light source.
Any factor other than the independent variable that differs across treatment groups is a potential confounding variable.
3
Determine if the varying factor (distance) could influence the dependent variable (photosynthesis rate).
Distance changes light intensity, which directly affects the rate of photosynthesis.
Because both the independent variable (color) and the confounding variable (distance/intensity) varied across groups, the student cannot determine which factor caused the observed changes in oxygen production.

Anahtar Kavram

Identifying Confounding Variables
Tahmini Süre:1m 30s
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Konular

Identifying Sources of Error and Confounding Variables

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