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Identifying VariablesIdentifying Variables
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DesigningDesigning
InvestigationsInvestigations

3 Kinds of Variables3 Kinds of Variables
 Independent Variable – somethingIndependent Variable – something
that is changed by the scientistthat is changed by the scientist
 What is testedWhat is tested
 What is manipulatedWhat is manipulated

 Dependent Variable – something thatDependent Variable – something that
might be affected by the change inmight be affected by the change in
the independent variablethe independent variable
 What is observedWhat is observed
 What is measuredWhat is measured
 The data collected during theThe data collected during the
investigationinvestigation

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

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

Identify the variables inIdentify the variables in
this investigation.this investigation.

What was the independentWhat was the independent
variable?variable?
Ages of the studentsAges of the students
Different ages were tested byDifferent ages were tested by
the scientistthe scientist

What was the dependent variable?What was the dependent variable?
The time it to put the puzzleThe time it to put the puzzle
togethertogether
The time was observed andThe time was observed and
measured by the scientistmeasured by the scientist

What was a controlled variable?What was a controlled variable?
Same puzzleSame puzzle
All of the participants wereAll of the participants were
tested with the same puzzle.tested with the same puzzle.
It would not have been a fairIt would not have been a fair
test if some had an easy 30test if some had an easy 30
piece puzzle and some had apiece puzzle and some had a
harder 500 piece puzzle.harder 500 piece puzzle.

Another example:Another example:

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

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

Independent variable:Independent variable:
Sizes of nailsSizes of nails
These were changed by theThese were changed by the
scientistscientist

Dependent variable:Dependent variable:
Number of paper clips pickedNumber of paper clips picked
upup
The number of paper clipsThe number of paper clips
observed and countedobserved 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

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

 Independent variable – temperatureIndependent variable – temperature
of waterof water
 Dependent variable – time to cookDependent variable – time to cook
an eggan egg
 Controlled variable – type of eggControlled variable – type of egg

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

 Independent variable – depth of theIndependent variable – depth of the
waterwater
 Dependent variable – temperatureDependent variable – temperature
 Controlled variable – thermometerControlled variable – thermometer

Designing InvestigationsDesigning Investigations

The greater the amount of soap in aThe greater the amount of soap in a
soap and water mixture, the bigger asoap and water mixture, the bigger a
soap bubble can be blown.soap bubble can be blown.
 Design an investigation to test thisDesign an investigation to test this
hypothesis.hypothesis.
 Identify the variablesIdentify the variables
 What exactly will be changed? HowWhat exactly will be changed? How
will it be changed?will it be changed?
 What exactly will be measured? HowWhat exactly will be measured? How
will it be measured?will it be measured?

The farther a ball drops, the higherThe farther a ball drops, the higher
it will bounce.it will bounce.
 Design an investigation to test thisDesign an investigation to test this
hypothesis.hypothesis.
 Identify the variablesIdentify the variables
 What exactly will be changed?What exactly will be changed?
How will it be changed?How will it be changed?
 What exactly will be measured?What exactly will be measured?
How will it be measured?How will it be measured?

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Identifying variables

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Identifying variables