If more than one variable changes at the same time in an experiment,
the outcome of the experiment may not be clearly attributable to any one
of the variables. It may not always be possible to prevent outside variables
from influencing the outcome of an investigation (or even to identify all
of the variables), but collaboration among investigators can often lead
to research designs that are able to deal with such situations.
| NSES Content Standard A
Science as Inquiry: Abilities necessary to do scientific inquiry Grades 5-8, page 145 Design and conduct a scientific investigation. Students should develop general abilities, such as systematic observation, making accurate measurements, and identifying and controlling variables. They should also develop the ability to clarify their ideas that are influencing and guiding the inquiry, and to understand how those ideas compare with current scientific knowledge. Students can learn to formulate questions, design investigations, execute investigations, interpret data, use evidence to generate explanations, propose alternative explanations, and critique explanations and procedures. NSES Content Standard A
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