3 Kinds of Variables

Identifying VariablesIdentifying Variables&&

Designing Designing InvestigationsInvestigations

Play the “variable song!”Play the “variable song!”

http://www.youtube.com/watch?v=Hxbz656Euyw




3 Kinds of Variables3 Kinds of Variables

Independent VariableIndependent Variable – something – something that is that is changedchanged by the scientist. by the scientist. What is What is tested ?tested ? What is What is manipulated?manipulated?


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

..


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

For Example:For Example:

Students of different ages Students of different ages were given the same jigsaw were given the same jigsaw

puzzle to put together. puzzle to put together. They were timed to see how They were timed to see how

long it took to finish the long it took to finish the puzzle.puzzle.

Let’s see what the Let’s see what the different variables are in different variables are in this puzzle investigation.this puzzle investigation.

What was the What was the independent independent variable?variable?

Ages of the studentsAges of the studentsDifferent ages were tested by Different ages were tested by

the scientistthe scientist

What was the What was the dependent variabledependent variable??

The time it to put the puzzle The time it to put the puzzle togethertogetherThe time was observed and The time was observed and

measured by the scientistmeasured by the scientist

What was a What was a controlled variablecontrolled variable??

Same puzzleSame puzzleAll of the participants were All of the participants were

tested with the same puzzle.tested with the same puzzle. It would not have been a fair It would not have been a fair

test if some had an easy 30 test if some had an easy 30 piece puzzle and some had a piece puzzle and some had a harder 500 piece puzzle.harder 500 piece puzzle.

Another example:Another example:

An investigation was done with An investigation was done with an electromagnetic system made an electromagnetic system made from a battery and wire wrapped from a battery and wire wrapped around a nail. Different sizes of around a nail. Different sizes of nails were used. The number of nails were used. The number of

paper clips the electromagnet paper clips the electromagnet could pick up was measured.could pick up was measured.

What are the variables in this What are the variables in this investigation?investigation?

Independent variable:Independent variable:

Sizes of nailsSizes of nailsThese were changed by the These were changed by the

scientistscientist

Dependent variable:Dependent variable:

Number of paper clips picked Number of paper clips picked upupThe number of paper clips The number of paper clips

observed and counted observed and counted (measured) (measured)

Controlled variables:Controlled variables:

Battery, wire, type of nailBattery, wire, type of nail None of these items were changedNone of these items were changed

One more:One more:

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

boil.boil.

Independent variable – temperature Independent variable – temperature of waterof water

Dependent variable – time to cook Dependent variable – time to cook an eggan egg

Controlled variable – type of eggControlled variable – type of egg

Last one:Last one:

The temperature of The temperature of water was measured at water was measured at

different depths of a different depths of a pond.pond.

Independent variable – depth of the Independent variable – depth of the waterwater

Dependent variable – temperatureDependent variable – temperature Controlled variable – thermometerControlled variable – thermometer

Now its your turn!Now its your turn!Rubber Band VariablesRubber Band Variables

Materials:Materials:Pencil Pencil Rubber bandRubber bandPaper clipPaper clipMasking tapeMasking tapeWashersWashersrulerruler

ProcedureProcedure Tape the pencil to your desk so that it hangs over the edge.Tape the pencil to your desk so that it hangs over the edge. Attach the paper clip to the rubber band.Attach the paper clip to the rubber band. Open one end of the rubber band to make a hook for the Open one end of the rubber band to make a hook for the

washers.washers. Hang the rubber band over the end of your pencil.Hang the rubber band over the end of your pencil. Measure the length of the rubber band in cm.Measure the length of the rubber band in cm. Record your data.Record your data. Place 1 washer on the paper clip “hook”.Place 1 washer on the paper clip “hook”. Measure and record the length of the rubber band again.Measure and record the length of the rubber band again. Continue adding washers, one washer at a time, and Continue adding washers, one washer at a time, and

measuring the rubber band until a total of 10 washers have measuring the rubber band until a total of 10 washers have been added.been added.

Line Graph and ConclusionLine Graph and Conclusion Using the graph paper provided, create a Using the graph paper provided, create a

line graph that represents your data.line graph that represents your data. Complete the conclusion questions.Complete the conclusion questions.

Let’s Review!Let’s Review!

http://www.youtube.com/watch?v=x2606GQmDqY&feature=related



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3 Kinds of Variables