Independent, Dependent, Constant Variables Independent, Dependent, Constant

Types of variables Constant (and Control… we will review this at the end)

Types of variables Constant

Design an Experiment about… Plants

Design an Experiment About… Plants What would be our dependent variable? What can we measure? How tall the plant grows How fast the plant grows The mass of the plant The size of the leaves The colour of the plant

Dependent Variable Our dependent variable is (pick ONE): How fast the plant grows Dependent variable: something you can’t control directly, but you can observe and measure

Types of variables Constant

Design an Experiment About… Plants What would be our independent variable? What can we change? The amount of water we give the plant The type of water we give the plant (salt water) The amount of sunlight the plant receives The amount of fertilizer (compost) The type of soil we use The amount of soil we use The type of plant The amount of nutrients we give the plant The temperature The depth you plant the seed The size of the seed you plant

Independent Variable Our independent variable is (pick ONE): The amount of fertilizer we give the plant Independent variable: something you are manipulating during your experiment, this will affect the dependent variable

Our variables are... Independent variable: The amount of fertilizer we give the plant Dependent variable: How fast the plant grows (You could have picked different variables from the list… there are usually LOTS of different options for variables! But for each experiment you will pick ONE VARIABLE to study.)

Purpose of the Experiment Independent variable Dependent variable Independent variable: The amount of fertilizer we give the plant Dependent variable: How fast the plant grows

Purpose of the Experiment Independent variable Dependent variable How will the amount of fertilizer we give the plant affect how fast the plant grows?

Hypothesis Independent variable Dependent variable BECAUSE _______________________________________________. Independent variable: The amount of fertilizer we give the plant Dependent variable: How fast the plant grows

Hypothesis Independent variable: The amount of fertilizer we give the plant Dependent variable: How fast the plant grows IF we give the plant fertilizer THEN the plant will grow faster BECAUSE the fertilizer will provide the plant with more nutrients.

Types of variables Constant: variables that stay the same, what you don’t change

Constant Variables How do we find our constant variables? Look at the list we came up with for independent variables. We picked ONE variable as our independent variable. This is the variable we are manipulating. Every other variable on the list… needs to stay constant (stay the same). Constant variable: things that you are NOT changing, they stay the same for everything in your experiment

Constant Variables Our constant variables are: The amount of water we give the plant The type of water we give the plant (salt water) The amount of sunlight the plant receives The type of soil we use The amount of soil we use The type of plant The amount of nutrients we give the plant The temperature The depth you plant the seed The size of the seed you plant

Constant Variables We want to know: How will the amount of fertilizer we give the plant affect how fast the plant grows? Example: we will keep the amount of water we give the plant constant. We will give all plants exactly the same amount of water. Why…? Our experiment is looking for the effects of fertilizer. If we change any other variables, we can’t tell what results are from the fertilizer! So everything else stays CONSTANT.

Control Control group: does not get the variable that is being tested Is the “opposite” of your hypothesis Example: our hypothesis is... if we give the plant fertilizer then… Opposite: If we DON’T give the plant fertilizer… Control group: plants that don’t get fertilizer