Identifying Variables

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Types of Variables There are 3 main types of variables: Independent Variable (IV): The variable that is changed or manipulated by the scientist; the ‘I control’ variable Dependent Variable (DV): The variable that might respond because of what the scientist changes – what is being measured Control Variable(s) (CV): The variable(s) that will stay the same throughout the experiment

Remember! Your hypothesis can TELL you what your variables are! Ex. If some students eat breakfast before school and others do not, then the ones who do eat breakfast will have better grades in their morning classes, because their brains have more energy to think. IV: Eating breakfast DV: Better grades in morning classes CV: test given

Use this hypothesis to identify the variables: Practice Use this hypothesis to identify the variables: 1. If 7th graders and 8th graders complete the same math problems, then the 8th graders will have more answers correct, because they have studied math for one year longer than the 7th graders. IV: ______________________ DV: ______________________ CV: ______________________

Now read the following experiment and identify the variables 2. Elizabeth wanted to test if temperature affected how fast milk goes bad and curdles. She left milk in a room temperature closet, a fridge, and a oven that was turned on low heat. She then measured how rotten the milk was after 10 days. IV: ____________________________________ DV: ____________________________________ CV: ____________________________________

Hypothesis Writing

Form a Hypothesis Hypothesis: an educated guess or prediction; an “if, then, because” statement If ____independent (manipulated) variable_____ then__dependent (responding) variable_____ because ___what you’ve observed, inferred or know to be true through scientific principle

Example: Independent Variable: Cat fed a lot of food Gained weight Control Variable: If _____________________________ then _______________________ because ____________________

How is the Variable changing? Try to use INCREASE and DECREASE in your hypothesis!* Ex. IF a cat receives an increase in the amount of food, THEN the animal will increase weight BECAUSE more calories are consumed. * Or similar words showing growth or loss

Remember Try to keep your statement in 3rd person This means no I, you, she, he, they etc. Ex. If dry bread and moist bread are left in bags for two weeks, then the moist bread will grow mold more quickly than the dry bread, because mold is a living organism, and organisms need water to survive

Your because statement should not restate your if statement. Avoid Circular Logic Your because statement should not restate your if statement. Ex. If I water my plant twice a day, then the plant will grow more quickly, because the plant is watered twice a day. If I water my plant twice a day, then the plant will grow more quickly, because organisms require moisture in order to survive.

Now Try it on Your Own! Come up with your own hypothesis related to cell phone usage. Identify your (IV, DV, CV). Add this in your Cornell notes