An introductory text reads, 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. Is 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.
An illustration below shows a smart phone that displays two chat boxes. The first chat box reads, to test the research question, you must control participants, variables, and study implementation and the second chat box reads, Research question: Does texting while driving cause accidents?
The smart phone is surrounded by three illustrations and associated callouts.
The first illustration labeled variables shows a car moving through a dashed arrow in between safety cone. The associated callout reads, independent variable: The variable that researchers deliberately manipulate. Example: The independent variable is texting while driving. Experimental group drives through obstacle course while texting. Control group drives through obstacle course without texting.
dependent variable: 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).
extraneous variable: 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.
The second illustration labeled study material shows 2 people with question marks. An associated callout reads, random assignment: Process by which researcher randomly assigns participants to experimental or control group. Example: Experimenter flips coin to determine participant’s group. experimenter bias: 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. When possible, researchers control for these effects by using a double-blind study in which neither researcher nor participant knows what group participants are assigned to.
The third illustration labeled participants shows 2 rows of people, where four of the people are highlighted. An associated callout reads, representative sample: 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. random sample: Method used to ensure participants do not introduce unexpected bias. Example: Researchers recruit participants by randomly selecting students from the college directory. Behind the text shows clipart icon of men and women are standing alternatively in series highlighted by green shades. The bubble and rectangular callouts are linked by dotted line with arrow head.