Question

In order to test whether caffeine intake affects the number of hours a person sleeps, Sophie recruited 120 subjects and randomly assigned them into one of three groups: (1) no caffeine intake, (2) 30 mg of caffeine per day, and (3) 50 mg of caffeine per day. She then asked the subjects to report how many hours they slept each night. Sophie's independent variable is ______________, and her dependent variable is ______________.

Answer 1

Answer:

Sophie's independent variable is amount of caffeine ingested

Her dependent variable is number of hours slept each night.

Explanation:

In scientific research, variables are factors, traits or results that have the possibilty of being expressed in different amounts in the experiment. There are three kinds of variables; the dependent, the independent and the controlled variables.

A independent variable is the variable that the experimenter can change at will, in this example the independent variable is the amount of caffeine taken by the study groups, for example 30mg or 50mg. The scientist has complete control over how the independent variable varies.

The dependent variable, is the result of the variation of the independent variable. This is actually the focus of the scientist and is usually the aim of carrying out the experiment. In the case of our example, the dependent variable is the length of time slept at night, which is a direct result of the quantity of coffee ingested. another example of dependent variable is to see how much the height of a growing child changes when comparing the effect of a new baby formula with an existing on.

Finally, the controlled variables are variables that are kept constant or uniform in both the subject groups and the control groups to avoid any bias from external factors other than the independent variable from having an effect on the dependent variable. In our example, one controlled variable can be the serenity of the sleeping environment, because noise and heat can affect the length of time one sleeps, so the scientist ensures that both people taking the different doses of the caffeine and those not taking at all, have the same sleeping environment to remove any interference caused by external factors on sleep.

you can think of other experiments and try to classify them into these three categories of variables, it'll help you understand better.