Controlled experiments involve manipulating one variable while keeping all others constant to test a hypothesis. To ensure accurate results, researchers must eliminate as many variables as possible. For example, to test the effect of sound on plants, researchers must use the same plant species, size, and location, and expose them to the same sound at the same time. A control group is also necessary to compare results. Conducting controlled experiments with humans is challenging due to their variability, requiring researchers to find similar groups for accurate results.
A controlled experiment is one in which strict control is exercised over variables, with one or more variables being changed or “manipulated” while all other variables remain the same. This is one of the hallmarks of many types of scientific investigation. When a hypothesis is tested, it will not be tested as well if there are multiple variables that could affect the outcome. Trying to create an environment where as many variables are eliminated can help make test results more believable.
If someone wanted to examine the plant’s response to a specific type of sound, there would be ways to set up a controlled experiment and ways to quickly get out of control. The person could take six plants and place each one in a different area of a house. He could then expose the plants to sound at different times of the day. It’s easy to see how many variables are at play: the plants aren’t in the same location, the sound doesn’t play at the same time of day, and the plants may not even be the same species.
To give more control over this experiment, the researcher could do several things. He could make sure that he bought plants of roughly the same size and definitely the same plant species, as well as keeping all the plants in the same position. This would mean that other factors such as different light exposure would not harm the results. The same sound should also be played at the same time.
Essentially, the goal would be to make everything look as similar as possible before starting testing. This allows the researcher to manipulate a single variable, sound exposure, to determine what effect it might have on plants. At the same time, the experiment must examine the behavior of plants without sound exposure.
Therefore, a sample of plants as similar as possible to the first group should be kept in a nearly identical environment. In this way, there is a basis for comparing the behavior of the plant when it is exposed to sound and the behavior of the plant when it is not. A second group that is not exposed to the manipulated variable is often called a control group.
Conducting a controlled experiment can be very difficult, as it is easy to overlook a variable and fail to control it. What is particularly challenging is attempting to study responses in humans in this way. Humans are variable: they come in different sizes, have different genetic markers, and exhibit a wide variety of behaviors. For things like drug studies, scientists may need to look for people with similarities in age, health profile, and many other areas, so the results aren’t skewed. They also need to find a similar group of people who will act as a control group and will not receive the drug or manipulated variable.
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