Running Experiments

Running An Experiment |
| Question: How many variables should one focus on in a typical experiment and why? |

| Two =2. If you look at just one variable, there would be no relationship to find. If you look a three or more variables, you would not know which variable was causing the changes in the other to occur. |

Dependenet and Independent Variables
| Question: How can you tell which of the two variables if the dependent and which is the independent?
| The independent varaible is controlled by the experimentor. It is independent in that it can be set to any value (if possible of course). The dependent variable is the one that is measured. It is dependent on the values set for the independent variable.
Confounding Variables
| In any experiment between two variables, it is almost always true that there are other variables that could effect the outcome of the experiment. These are called confounding variables.
| Question: How can we keep confounding variables from confusing the results of our experiment?

Example Experiment |  |
| We are interested in seeing how fast a plant will grow. We set up an experiment where we measure the height of the plant in centimeters once each day.

| Question: What are the independent, dependent, and several possible confounding variables?
| The independent variable is the time, since it is set at once a day. The dependent variable is the height, since that is measured. A few of the possible confounding variables are light intensity, amount of water, humidity, temperature. and time of year. |
| By keeping them constant. If they do not change, they should not cause the variables in the experiment to change. |

Design An Experiment Exercise
| Describe an experiment with two variables different than those discussed in class. Note which is the dependent and which is the independent variable. List several possible confounding variables.