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Identifying Variables��

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Kinds of Variables

  • Independent Variable – something that is changed by the scientist
    • What is tested
    • What is manipulated

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Kinds of Variables

  • Dependent Variable – something that might be affected by the change in the independent variable
    • What is observed
    • What is measured
    • The data collected during the investigation

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Kinds of Variables

  • Controlled Variable – a variable that is not changed
    • Also called constants
    • Allow for a “fair test”

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CONTINUOUS

DISCRETE

NOMINAL

ORDINAL

RATIO

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For Example:

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Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle.

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Identify the variables in this investigation.

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What was the independent variable?

  • Ages of the students
    • Different ages were tested by the scientist

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What was the dependent variable?

  • The time it to put the puzzle together
    • The time was observed and measured by the scientist

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What was a controlled variable?

  • Same puzzle
    • All of the participants were tested with the same puzzle.
    • It would not have been a fair test if some had an easy 30 piece puzzle and some had a harder 500 piece puzzle.

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Another example:

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An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different sizes of nails were used. The number of paper clips the electromagnet could pick up was measured.

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What are the variables in this investigation?

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Independent variable:

  • Sizes of nails
    • These were changed by the scientist

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Dependent variable:

  • Number of paper clips picked up
    • The number of paper clips observed and counted (measured)

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Controlled variables:

  • Battery, wire, type of nail
    • None of these items were changed

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One more:

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The higher the temperature of water, the faster an egg will boil.

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  • Independent variable – temperature of water
  • Dependent variable – time to cook an egg
  • Controlled variable – type of egg

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Last one:

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The temperature of water was measured at different depths of a pond.

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  • Independent variable – depth of the water
  • Dependent variable – temperature
  • Controlled variable – thermometer