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發表於 2006-5-12 18:39:56
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原帖由 Dadadede 於 2006-5-11 05:59 PM 發表
what is dependent variable?what is independent variable?
Variables & Hypothesis
Variables
Scientists use an experiment to search for cause and effect relationships in nature. In other words, they design an experiment so that changes to one item cause something else to vary in a predictable way.
These changing quantities are called variables, and an experiment usually has three kinds: independent, dependent, and controlled.
The independent variable is the one that is changed by the scientist. In an experiment there is only one independent variable.
As the scientist changes the independent variable, he or she observes what happens.
The dependent variable changes in response to the change the scientist makes to the independent variable. The new value of the dependent variable is caused by and depends on the value of the independent variable. For example, if you open a faucet (the independent variable), the quantity of water flowing (dependent variable) changes in response--the water flow increases. The number of dependent variables in an experiment varies, but there is often more than one.
Experiments also have controlled variables. Controlled variables are quantities that a scientist wants to remain constant, and he must observe them as carefully as the dependent variables. For example, if we want to measure how much water flow increases when we open a faucet, it is important to make sure that the water pressure (the controlled variable) is held constant. That's because both the water pressure and the opening of a faucet have an impact on how much water flows. If we change both of them at the same time, we can't be sure how much of the change in water flow is because of the faucet opening and how much because of the water pressure. Most experiments have more than one controlled variable. Some people refer to controlled variables as "constant variables."
http://www.sciencebuddies.org/mentoring/project_variables.shtml |
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發表於 2006-5-11 21:21:35
發表於 2006-5-12 23:26:06
