The Scientific Method and Variables In every experiment, a scientist is trying to explore a problem or answer a question. To do this, you are testing the relationship between two different things called variables. Example: Does water temperature affect how much goldfish eat? In every experiment, there is one factor that you are testing. You change it on purpose and want to see what will happen as a result. You can think I DO. The independent variable is the factor that a scientist purposely in an experiment. In every experiment, there is one factor that you are trying to manipulate. You collect data about how the dependent variable changes. The dependent variable is the factor that a scientist or in an experiment. Independent variable: (what am I CHANGING in this experiment? Example: Does water temperature affect how much goldfish eat? Dependent variable: (what am I MEASURING and observing?) Snappy Practice: 1. The independent variable is abbreviated with letters. 2. The dependent variable is the part of the experiment you. 3. The independent variable is the part of the experiment you. 1
Constants The scientist only changes one variable (the independent variable) and measures one variable (the dependent variable). EVERYTHING ELSE IN THE EXPERIMENT MUST BE KEPT THE SAME! Factors that the scientist keeps the in an experiment are called. Example: Does water temperature affect much goldfish move? Constants: (what should I KEEP THE SAME in this experiment to make sure I am only testing the temperature?) NEURON CHECK.On your own: Does the color of a light bulb affect plant growth? A scientist places plants under different colored light bulbs for two weeks. They measured the growth of each plant every two days. Constants (two) Does the color of a candle affect how fast it burns? A scientist lit five different colored birthday candles at the same time. He timed how long each candle burned. Constants (two) 2
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Name: Score: / Grace decides to investigate the relationship between the cost of floor wax and how many scratches are on the floor. She applies each brand of wax to half of the classroom floor. She walks across each half of the room 100 times and counts the number of scratches to see which wax had the best protection. 1. What is the independent variable in Grace s experiment? 2. What is the dependent variable in Grace s experiment? 3. In his experiment, Grace kept the amount of wax used, the person walking on the floor, and the number of times they walked on the floor the same. All of these factors that Grace kept the same, are called: a. independent variables b. rules c. constants 4. Why should Grace keep so many things the SAME in his experiment? (Complete sentence) Name: Score: / Grace decides to investigate the relationship between the cost of floor wax and how many scratches are on the floor. She applies each brand of wax to half of the classroom floor. She walks across each half of the room 100 times and counts the number of scratches to see which wax had the best protection. 1. What is the independent variable in Grace s experiment? 2. What is the dependent variable in Grace s experiment? 3. In his experiment, Grace kept the amount of wax used, the person walking on the floor, and the number of times they walked on the floor the same. All of these factors that Grace kept the same, are called: a. independent variables b. rules c. constants 4. Why should Grace keep so many things the SAME in his experiment? (Complete sentence) 4
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