Conducting Experiments
The foundation of science knowledge is based on experimentation. Experiments are carefully designed to assure that results can be clearly interpreted. In conducting experiments, it is extremely important that all variables be very precisely defined, measured and controlled. In the laboratory experiments in this course, you will need to identify, measure and control specific variables like a scientist would do.
The first step of an experiment is to come up with a question based on an observation. For example, you might ask “Does the amount of nitrogen in the soil in my garden have an impact on the number of tomatoes on the vine?”. You would then develop a testable hypothesis statement. For example, “I hypothesize that the number of tomatoes in my garden will be low when the content of nitrogen in the soil is low.”
Independent variable
You will set the value of this variable (for example, the amount of nitrogen in the soil) it can be set to different values (for example, nitrogen levels could be low, medium, and high).
Dependent variable
The value of the variable will vary depending the value of the independent variable (for example, the number of tomatoes on the vine will be high when the amount of nitrogen is medium, but the number of tomatoes on the vine will be low when the amount of nitrogen is low and high). The value of this variable is the main experimental result. As part of a hypothesis statement, you would state how the independent variable will impact the dependent variable.
Control variable
You will set these values so that they do not change. By keeping these variables constant, you assure that they do not impact either the independent variable or the dependent variable (for example, if you set up three different test gardens for low, medium and high nitrogen soil levels, you will want to make sure that all three gardens receive the same amount of water and sunlight. In this case, water and sunlight would be the variables that you control.).