Variables in an investigation are things that can change. Variables include the environment where the experiment is performed, thus light, temperature and humidity might affect the experimental results. But, if these variable stay the same, they are called controlled variables. Controlled variables are assumed to not affect the results of the experiment.
In a cause/effect investigation, you want only two variables to change. One of the variables is called the independent variable. The independent variable will cause the other variable, called the dependent variable, to change.
Independent Variable Affects (cause to change) > Dependent Variable
You need a variable that is affected by eye color. You also need a variable that you can measure how it changes.
You could use online reaction tests, such as:
Your question is: What effect does eye color have on reaction time?
Well, what do you think? Don’t just guess. Instead, do a little more research. Reaction time is critical in racing. Find out which athletes have the fastest reaction time and what is their eye color.
Record your data: The more data collected, the more credible will be your conclusion. It only takes a few minutes to take the reaction tests online. Get as many people as possible to measure their reaction time for you. You might use three or more separate data collecting sheets. Average the reaction time for each eye color and make a bar graph. Remember that independent variables are on the horizontal and dependent variables on the vertical line of graphs.