Write this in your notebook as your heading

Write this in your notebook as your heading Variables What makes an experiment “fair”?

Write this in your notebook as your heading Variables A variable is something that changes in an experiment

Science experiments use… Independent Variable (manipulated): the one and only factor that is changed in an experiment. Dependent Variable(responding): the factor which is measured/observed in the experiment. Responds to changes in the independent variable. Controlled variables (constants): all the factors that stay the same in an experiment Write this in your notebook

An example: Imagine you want to see what color of bird feeders your local birds preferred. Red? Blue? Green? Yes, also write this. You will thank me later

Variables Independent Variable: color of the feeders Dependent Variable: amount of seed eaten/number of birds Controlled (constants): everything else that is kept the same, for example: – the location of the feeders – the kind of feeder used – putting the feeders out at the same time

Create and fill out this data table in your notes Our Experimental Design Controlled variables Location of feeders Kind of seed Type of feeder Independent Variable Red Dependent Variable Copy this into your notebook Amount of Seed Eaten/number of birds Blue Green Amount of Seed Amount of Eaten/number Seed of birds Eaten/numbe r of birds

If everything except the independent variable is held constant, we can say: The experiment is FAIR. (ONLY the independent variable can change!)

Is Sam’s experiment fair? YES? NO?

Why is it important to change only 1 thing at a time?

If you don’t… then you won’t know what is causing your results. Independent Variable

What do you think? Terry loves birds and wants to see as many as she can in her yard. She wants to know whether she is wasting money buying an expensive mixed seed, when a cheaper brand just arrived at her local store. She wonders… will the expensive seed attract more birds to her back yard? Talk with your group and determine the following: 1. Independent variable 2. Dependent variable 3. Controlled variables (constants)

Terry’s Experimental Design Independent Variable ? Dependent Variable ? Constants ?

Terry’s Experimental Design Independent Variable Kind of seed: Expensive feed Cheap feed Dependent Variable Number of birds that visit Constants Location of feeders Type of feeder Way she measures the amount of seed eaten and the way she counts birds $