Instructions We can frequently notice that certain events in our everyday life correlate with each other.

Instructions

We can frequently notice that certain events in our everyday life correlate with each other. Some of these correlations are very straightforward and causative, meaning that the change in one event causes the change in another event. For example, the more guests we expect at a pizza party, the more pizza we have to make or order. An increase in the number of guests causes an increase in the amount of pizza needed. It is a positive causative correlation where the number of guests directly affects the amount of pizza needed. We can also correlate the number of guests with the amount of after-party pizza leftovers and it is likely to be a negative causative correlation, where the more guests we had, the less leftovers we will have left.

In the scientific world (and, in many cases, in everyday life), experiments are designed to search for cause and effect relationships between events with the purpose of finding those causative relationships. To this end, variables are used. Variables are measurable components of an experiment. A variable is any changing factor, trait, or condition that can exist in differing amounts or types. An experiment usually has three kinds of variables: independent, dependent, and controlled.

For a person designing and (or) conducting an experiment, these three types of variables address different questions:

• Independent variable(s) answers the question, "What do I change?" Their values are controlled or selected by the experimentator.
• Dependent variable(s) answers the question, "What do I observe?" The dependent variable can change in response to independent variable.
• Controlled variable(s) answers the question, "What do I keep the same?" These are the variables that are kept constant.

In addressing the question, "Does the temperature of water affect the amount of salt that can be dissolved in it?" we can identify the following variables:

• Independent Variable: Water temperature
• Dependent Variable: The amount of salt we are able to dissolve
• Controlled Variable: The type of salt; the volume of water

Practice Assignment

You have created a new fertilizer, "SuperGrow," and would like to study its effect on your basil plants. Briefly describe your experimental design (80-100 words) and determine the independent, dependent, and control variables in your experiment.