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JOAN CARTAN-HANSEN, HOST: WHEN

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YOU USE THE SCIENTIFIC METHOD TO 
ANSWER A QUESTION, YOU START

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WITH AN EXPERIMENT.

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AND YOU DESIGN YOUR EXPERIMENT 
TO USE VARIABLES.

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THERE ARE THREE KINDS OF 
VARIABLES: INDEPENDENT,

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DEPENDENT AND CONTROLLED.

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LET'S SAY YOU WANT TO TEST IF A 
BIG DOG EATS MORE THAN A SMALL

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DOG.

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THE INDEPENDENT VARIABLE IS THE 
THING YOU CHANGE IN THE

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EXPERIMENT.

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IN THIS CASE, THE BIG DOG AND 
THE SMALL DOG.

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THE DEPENDENT VARIABLE IS ONE 
YOU MEASURE.

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IN OUR EXPERIMENT, IT'S THE 
AMOUNT OF FOOD EACH DOG EATS.

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THE CONTROLLED VARIABLES ARE THE 
THINGS YOU WANT TO REMAIN THE

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SAME OR CONSTANT.

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IN THIS EXPERIMENT, YOU WOULD 
WANT TO MAKE SURE THE DOGS EAT

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AT THE SAME TIME, 
EAT THE SAME FOOD, AND HAVE NOT

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EATEN FOR THE SAME AMOUNT OF 
TIME BEFORE THE EXPERIMENT.

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ONCE YOU'VE IDENTIFIED YOUR 
VARIABLES, YOU'RE READY FOR THE

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EXPERIMENT.

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AND YOUR DOGS ARE READY FOR 
DINNER.

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FOR MORE INFORMATION ABOUT 
INVENTIONS AND THE SCIENTIFIC

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METHOD, CHECK OUT THE SCIENCE 
TREK WEBSITE.

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YOU'LL FIND IT AT 
IDAHOPTV.ORG/SCIENCE TREK

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