Warmup 8/23/2016 Write down all the factors you can think of that affect how much a plant grows

Scientific Method - Variables

What affects plant growth? Water Soil (nutrients) Fertilizer Composition Light Duration Intensity Color These are all variables for plant growth

What do the variables affect? What do those variables (water, soil, light) change? Height Growth Rate Lifespan Products (e.g. fruit) These are all variables too

What is a variable? There are types of variables: Independent Variable The variable that is changed (manipulated) by you, the scientist the ‘I control’ variable Dependant Variable The result of what you changed Depends on the independent variable

What is a variable? There are types of variables: Independent Variable Changed by the scientist An experiment usually has only one independent variable Dependant Variable Measured by the scientist (what you collect data about) Results usually come from observing dependent variables

Find the Variables A study was done to find if different tire treads affect the braking distance of a car. Independent Variable? (What is the scientist changing intentionally each time?) Dependent Variable? (What is the scientist trying to prove?)

Find the Variables Students of different ages were given the same puzzle to assemble. The puzzle assembly time was measured. Independent Variable? (What is being changed in the experiment intentionally?) Dependent Variable? (What is going to be affected by the change?)

Example – A baker A baker wants to see if adding chocolate chips to her famous peanut butter cookies will make them sell better. So she changes the recipe and advertises her new cookies Independent Variable? (What is the baker changing intentionally in each trial?) Dependent Variable? (What result is the baker looking for?)

Let’s look at the results After # of Chips Cookies sold 10 148 20 188 30 174 40 75 Before # of Chips Cookies sold 100 What do you conclude about adding chocolate chips?

Let’s look at the results After # of Chips Cookies sold 10 148 20 188 30 174 40 75

Let’s try again The cookies with 0 chips are called the control group Before # of Chips Cookies sold 100 After # of Chips Cookies sold 250 10 150 20 175 The cookies with 0 chips are called the control group

What variable did we miss? A baker wants to see if adding chocolate chips to her famous peanut butter cookies will make them sell better. So she changes the recipe and advertises her new cookies Independent Variable? (What is the baker changing intentionally in each trial?) Dependent Variable? (What result is the baker looking for?)

Definitions Independent Variable How will you remember? The variable that is changed by the you, the scientist Dependant Variable The result of what you changed

Remember! Your hypothesis can TELL you what your variables are! Ex. If I drink Mountain Dew before bed, then I will not sleep very much. IV: DV:

Use this hypothesis to identify the variables: Practice Use this hypothesis to identify the variables: If I leave all the lights on all day, then my electric bill will be expensive IV: ______________________ DV: ______________________

In every experiment, there are two groups: Control Experimental There should be one difference The independent variable

Can you conclude that the independent variable caused the dependent variable?

Claim: Ice cream causes sunburns As ice cream consumption increases, so do frequency of sunburns