The introductory text reads as follows: “The experimental method is the type of research that can tell us about causes and effects. It is different from descriptive studies in that key aspects of the experiment—participants, variables, and study implementation—are tightly controlled. The experiment typically includes at least two groups—an experimental group and a control group. This allows the researcher to isolate the effects of manipulating a single variable, called the independent variable. Imagine you want to know if laws that ban texting while driving are worthwhile. Does texting really cause more accidents? Perhaps texting is merely correlated with higher accident rates in certain populations, such as college students, because college students are both more likely to text and more likely to have accidents. In order to find out, you have to perform an experiment.”
At the center of the infographic is a graphic of a phone with two messages on the screen. The top message reads, “Research question: Does texting while driving cause accidents?” The second message reads, “To test the research question, you must control participants, variables, and study implementation.” Three balloons lead from the phone graphic to the three sections of the infographic. At the top, a graphic labeled “VARIABLES” shows a car following a path among traffic cones. The text to the right follows:
The variable that researchers deliberately manipulate. Example: The independent variable is texting while driving.
The variable measured as an outcome of manipulation of the independent variable. Example: The dependent variable is the number of accidents (objects hit in obstacle course).
An unforeseen factor or characteristic that could interfere with the outcome. Example: Some participants have more driving experience than others. Without controlling the amount of driving experience, we can't be certain the independent variable caused more accidents. To the left of the phone graphic is a graphic labeled “PARTICIPANTS.” The graphic shows several rows of small stick figures with several green figures identified with arrows. A callout from one of the green figures leads to the text, which reads as follows:
Subset of the population chosen to reflect population of interest. Example: Participants must be college students. Other groups might be affected differently by the independent variable.
Method used to ensure participants do not introduce unexpected bias. Example: Researchers recruit participants by randomly selecting students from the college directory.
To the right of the phone graphic is a graphic labeled “STUDY IMPLEMENTATION,” showing two figures each labeled “?” The text reads as follows:
Process by which researcher randomly assigns participants to experimental or control group. Example: Experimenter flips coin to determine participant’s group.
Researchers’ expectations and unintentional behaviors can unwittingly change the outcome of a study. Example: Without thinking, researcher says “good luck” to one group. This might unintentionally cause them to try harder. Researchers control for these effects by using a double-blind study in which neither researcher nor participant knows what group participants are assigned to.