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Identifying Variables. Kinds of Variables Independent Variable – something that is changed by the...
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Transcript of Identifying Variables. Kinds of Variables Independent Variable – something that is changed by the...
Identifying VariablesIdentifying Variables
Kinds of VariablesKinds of Variables
Independent Variable Independent Variable – something – something that is changed by the scientistthat is changed by the scientist What is testedWhat is tested What is manipulatedWhat is manipulated Changed on purpose to see what may Changed on purpose to see what may
happenhappen
Kinds of VariablesKinds of Variables
Dependent Variable Dependent Variable – something that – something that might be affected by the change in might 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 the The data collected during the
investigationinvestigation
Kinds of VariablesKinds of Variables
Controlled Variable Controlled Variable – a variable that – a variable that is not changedis not changed Also called constantsAlso called constants Allow for a Allow for a ““fair testfair test””
The Bread ExperimentThe Bread Experiment
LetLet’’s discuss variables, constants and s discuss variables, constants and controls using the bread experiment!controls using the bread experiment!
Problem/QuestionProblem/Question
John watches his John watches his grandmother bake grandmother bake bread. He asks his bread. He asks his grandmother what grandmother what
makes the bread rise.makes the bread rise.
She explains that yeast She explains that yeast releases a gas as it releases a gas as it
feeds on sugar.feeds on sugar.
Problem/QuestionProblem/Question
John wonders if the John wonders if the amount of sugar used amount of sugar used in the recipe will affect in the recipe will affect the size of the bread the size of the bread
loaf?loaf?
HypothesisHypothesis
The hypothesis is an educated The hypothesis is an educated guess about the relationship guess about the relationship
between the independent and between the independent and dependent variables.dependent variables.
Note: These variables will be Note: These variables will be defined in the next few slides.defined in the next few slides.
Do you know the difference Do you know the difference between the independent and between the independent and
dependent variables?dependent variables?
Independent VariableIndependent Variable The independent, or The independent, or
manipulated variable, is a factor manipulated variable, is a factor thatthat’’s intentionally varied by the s intentionally varied by the
experimenter.experimenter.John is going to use 25g., 50g., John is going to use 25g., 50g.,
100g., 250g., 500g. of sugar in 100g., 250g., 500g. of sugar in his experiment.his experiment.
Dependent VariableDependent Variable The dependent, or responding The dependent, or responding variable, is the factor that may variable, is the factor that may change as a result of changes change as a result of changes
made in the independent made in the independent variable.variable.
In this case, it would be the size In this case, it would be the size of the loaf of bread.of the loaf of bread.
Control GroupControl Group
In a scientific experiment, the In a scientific experiment, the control is the group that serves control is the group that serves as the standard of comparison.as the standard of comparison.
The control group may be a The control group may be a ““no no treatment" or an treatment" or an ““experimenter experimenter
selectedselected”” group. group.
Control GroupControl Group
The control group is exposed to The control group is exposed to the same conditions as the the same conditions as the
experimental group, except for experimental group, except for the variable being tested.the variable being tested.
AllAll experiments should have a experiments should have a control group.control group.
Control GroupControl Group
Because his grandmother Because his grandmother always used 50g. of sugar in always used 50g. of sugar in
her recipe, John is going to use her recipe, John is going to use that amount in his control that amount in his control
group.group.
ConstantsConstants
John has to keep all John has to keep all other factors the same other factors the same so that any observed so that any observed changes in the bread changes in the bread can be attributed to can be attributed to the variation in the the variation in the amount of sugar.amount of sugar.
ConstantsConstants
The constants in an The constants in an experiment are all the experiment are all the
factors that the factors that the experimenter attempts experimenter attempts
to keep the same. to keep the same.
Can you think of some Can you think of some constants for this constants for this
experiment?experiment?
ConstantsConstantsThey might include:They might include:
Other ingredients to the Other ingredients to the bread recipe, oven used, bread recipe, oven used,
rise time, brand of rise time, brand of ingredients, cooking time, ingredients, cooking time,
type of pan used, air type of pan used, air temperature and humidity temperature and humidity
where the bread was where the bread was rising, oven temperature, rising, oven temperature,
age of the yeast… age of the yeast…
Another Example:Another 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.
Identify the variables in Identify the variables in this investigation.this investigation.
What was the independent What was the 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 dependent variable?What was the dependent 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 controlled variable?What was a controlled 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.
Yet Another example:Yet 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
Guess what?Guess what?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 egg and Controlled variable – type of egg and amount of wateramount of water
Last one:Last one:(I promise)(I promise)
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 – thermometer Controlled variable – thermometer
and pondand pond
Designing InvestigationsDesigning Investigations
The greater the amount of soap in a The greater the amount of soap in a soap and water mixture, the bigger a soap and water mixture, the bigger a
soap bubble can be blown.soap bubble can be blown. Design an investigation to test this Design an investigation to test this
hypothesis.hypothesis. Identify the variablesIdentify the variables What exactly will be changed? How What exactly will be changed? How
will it be changed?will it be changed? What exactly will be measured? How What exactly will be measured? How
will it be measured?will it be measured?
VariablesVariables
Independent Independent Variable- soapVariable- soap
Dependent Dependent Variable- size of Variable- size of bubble blownbubble blown
Controlled Controlled Variable-water and Variable-water and type of soaptype of soap
Amount of soap in Amount of soap in water mixturewater mixture
Size of the bubble Size of the bubble blown with different blown with different amounts of soap in amounts of soap in the waterthe water
The farther a ball drops, the higher The farther a ball drops, the higher it will bounce.it will bounce.
Design an investigation to test this Design 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?
VariablesVariables
Independent Independent Variable- length of Variable- length of fallfall
Dependent Variable-Dependent Variable-height of bounceheight of bounce
Controlled Variable- Controlled Variable- ball, surface, size of ball, surface, size of the ballthe ball
The length of the fall, The length of the fall, different fall for each different fall for each trialtrial
The height of the The height of the bounce from the bounce from the different lengths of different lengths of the fall ~ the higher the fall ~ the higher the height of the fall the height of the fall the higher the the higher the bouncebounce