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What Is An Experimental Group In Psychology

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Positive And Negative Controls

control and experimental groups

Positive and negative controls are two other types of control groups:

  • Positive control groups are control groups in which the conditions guarantee a positive result. Positive control groups are effective to show the experiment is functioning as planned.
  • Negative control groups are control groups in which conditions produce a negative outcome. Negative control groups help identify outside influences which may be present that were not unaccounted for, such as contaminants.

Why Are Control Groups Used In Experiments

A control group is used in an experiment as a point of comparison. By having a group that does not receive any sort of treatment, researchers are better able to isolate whether the experimental treatment did or did not affect the subjects who received it.

Participants in an experiment do not know if they are in the control group or the experimental group. Members of the control group often are given placebos. This allows researchers to more accurately identify the effectiveness of what is being studied.

Risks From Invalid Control Groups

If your control group differs from the treatment group in ways that you havenât accounted for, your results may reflect the interference of confounding variables instead of your independent variable.

Since those who come from a family of smokers are more likely to be exposed to secondhand smoke, a known cause of cancer, higher rates may occur among individuals in your treatment group, but you canât know for sure if this difference is due to the use of e-cigarettes.

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A Closer Look At Experimental Groups

Imagine that you want to do an experiment to determine if listening to music while working out can lead to greater weight loss. After getting together a group of participants, you randomly assign them to one of three groups. One group listens to upbeat music while working out, one group listens to relaxing music, and the third group listens to no music at all. All of the participants work out for the same amount of time and the same number of days each week.

In this experiment, the group of participants listening to no music while working out is the control group. They serve as a baseline with which to compare the performance of the other two groups. The other two groups in the experiment are the experimental groups. They each receive some level of the independent variable, which in this case is listening to music while working out.

In this experiment, you find that the participants who listened to upbeat music experienced the greatest weight loss result, largely because those who listened to this type of music exercised with greater intensity than those in the other two groups. By comparing the results from your experimental groups with the results of the control group, you can more clearly see the impact of the independent variable.

What Is Control Group Example


A simple example of a control group can be seen in an experiment in which the researcher tests whether or not a new fertilizer has an effect on plant growth. The negative control group would be the set of plants grown without the fertilizer, but under the exact same conditions as the experimental group.

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Major Schools Of Thought

Psychologists generally consider biology the substrate of thought and feeling, and therefore an important area of study. Behaviorial neuroscience, also known as biological psychology, involves the application of biological principles to the study of physiological and genetic mechanisms underlying behavior in humans and other animals. The allied field of comparative psychology is the scientific study of the behavior and mental processes of non-human animals. A leading question in behavioral neuroscience has been whether and how mental functions are localized in the brain. From Phineas Gage to H.M. and Clive Wearing, individual people with mental deficits traceable to physical brain damage have inspired new discoveries in this area. Modern behavioral neuroscience could be said to originate in the 1870s, when in France Paul Broca traced production of speech to the left frontal gyrus, thereby also demonstrating hemispheric lateralization of brain function. Soon after, Carl Wernicke identified a related area necessary for the understanding of speech.:202

Examples Of Control Groups In Experiments And Research

The control group in an experiment is the group that does not receive any treatment. It is used as a benchmark against which other test results are measured. This group includes individuals who are very similar in many ways to the individuals who are receiving the treatment, in terms of age, gender, race, or other factors. Explore control group examples to get a better handle on what a control group is.

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What Are Groups In Experiment Design

An experimental group is a test sample or the group that receives an experimental procedure. This group is exposed to changes in the independent variable being tested. The values of the independent variable and the impact on the dependent variable are recorded. An experiment may include multiple experimental groups at one time.

A control group is a group separated from the rest of the experiment such that the independent variable being tested cannot influence the results. This isolates the independent variable’s effects on the experiment and can help rule out alternative explanations of the experimental results.

While all experiments have an experimental group, not all experiments require a control group. Controls are extremely useful where the experimental conditions are complex and difficult to isolate. Experiments that use control groups are called controlled experiments.

Example Of An Experimental Group

Experimental Design in Psychology (AQA A Level)

Assume you want to study to determine if listening to different types of music can help with focus while studying.

You randomly assign participants to one of three groups: one group that listens to music with lyrics, one group who listens to music without lyrics, and another group that listens to no music.

The group of participants listening to no music while studying is the control group and the groups listening to music, whether with or without lyrics, are the two experimental groups.

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What Are The Unique Characteristic Of Qualitative Research

The real-world setting is the first characteristic of qualitative research. In qualitative research methods like observation method, ethnographic research, focus group, one-to-one interviews, the behavior of the participants of study is observed, and the conclusion is drawn based on their answers and their behavior.

Why A Control Group Is Important

While the control group does not receive treatment, it does play a critical role in the experimental process. This group serves as a benchmark, allowing researchers to compare the experimental group to the control group to see what sort of impact changes to the independent variable produced.

Because participants have been randomly assigned to either the control group or the experimental group, it can be assumed that the groups are comparable.

Any differences between the two groups are therefore the result of the manipulations of the independent variable. The experimenters carry out the exact same procedures with both groups with the exception of the manipulation of the independent variable in the experimental group.

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Examples Of Medication Testing Using Control Groups

Control groups are commonly used when pharmaceutical companies test new medications for physical health or psychological health. Subjects are screened to ensure they are appropriate candidates for the experiment. Those who are accepted to participate are randomly assigned to either an experimental group or the control group.

Types Of Control Groups

Research design
  • Positive Control Group
  • A positive control group is an experimental control that will produce a known response or a desired effect.
  • A positive control is used to ensure the success of a test and confirm the validity of an experiment.
  • For example, when testing for a new medication, an already commercially available medication could serve as the positive control.
  • Negative Control Group
  • A negative control group is an experimental control that does not result in the desired outcome of the experiment.
  • A negative control is used to ensure that there is no response to the treatment and help identify the influence of external factors on the test.
  • An example of a negative control would be the use of a placebo when testing for a new medication.
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    Importance Of Control Groups

    Control groups help ensure the internal validity of your research. You might see a difference over time in your dependent variable in your treatment group. However, without a control group, it is difficult to know whether the change has arisen from the treatment. It is possible that the change is due to some other variables.

    If you use a control group that is identical in every other way to the treatment group, you know that the treatmentâthe only difference between the two groupsâmust be what has caused the change.

    For example, people often recover from illnesses or injuries over time regardless of whether theyâve received effective treatment or not. Thus, without a control group, itâs difficult to determine whether improvements in medical conditions come from a treatment or just the natural progression of time.

    What Defines Experimental Psychology

    Defining any scientific field is in itself no exact science there are inevitably aspects that will be missed. However, experimental psychology features at least three central components that define it: empiricism, falsifiability, and determinism. These features are central to experimental psychology but also many other fields within science.

    Empiricism refers to the collection of data that can support or refute a theory. In opposition to purely theoretical reasoning, empiricism is concerned with observations that can be tested. It is based on the idea that all knowledge stems from observations that can be perceived, and data surrounding them can be collected to form experiments.

    Falsifiability is a foundational aspect of all contemporary scientific work. Karl Popper, a 20th century philosopher, formalized this concept that for any theory to be scientific there must be a way to falsify it. Otherwise, ludicrous, but unprovable claims could be made with equal weight as the most rigorously tested theories.

    For example, the Theory of Relativity is scientific, for example, because it is possible that evidence could emerge to disprove it. This means that it can be tested. An example of an unfalsifiable argument is that the earth is younger than it appears, but that it was created to appear older than it is any evidence against this is dismissed within the argument itself, rendering it impossible to falsify, and therefore untestable.

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    A Simple Example Of A Controlled Experiment

    A simple example of a controlled experiment may be used to determine whether or not plants need to be watered to live. The control group would be plants that are not watered. The experimental group would consist of plants that receive water. A clever scientist would wonder whether too much watering might kill the plants and would set up several experimental groups, each receiving a different amount of water.

    Sometimes setting up a controlled experiment can be confusing. For example, a scientist may wonder whether or not a species of bacteria needs oxygen in order to live. To test this, cultures of bacteria may be left in the air, while other cultures are placed in a sealed container of nitrogen or deoxygenated air . Which container is the control? Which is the experimental group?

    Careers In Experimental Psychology

    Experimental Groups and Control Groups (Examples from Xamplr)

    According to the American Psychological Association, experimental psychologists seek to answer basic questions about human behavior through applied research.

    For example, the most popular research topics include memory, emotion, perception and sensation. These scientific professionals typically work in university research centers, but also work for private companies or even the government. They may also work in other subfields, such as education, human resources and health care.

    Whatever the work setting, you will need a doctorate in psychology to be an experimental psychologist. Whats more, youll need to specialize in a particular area of research and pursue post-doctoral studies in that area.

    The job outlook for psychology as a whole is about average for the next few years. The Bureau of Labor Statistics estimates that all psychology jobs will grow at a rate of three percent through 2029. The BLS doesnt provide data specific to experimental psychology, but its reasonable to assume that job growth in this field will be on par with the field of psychology as a whole.

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    What Is Difference Between Experimental Group And Control Group

    Frequently asked questions about control groups. What is the difference between a control group and an experimental group? An experimental group, also known as a treatment group, receives the treatment whose effect researchers wish to study, whereas a control group does not. They should be identical in all other ways.

    Other Types Of Studies

    Surveys are used in psychology for the purpose of measuring attitudes and traits, monitoring changes in mood, and checking the validity of experimental manipulations . Psychologists have commonly used paper-and-pencil surveys. However, surveys are also conducted over the phone or through e-mail. Web-based surveys are increasingly used to conveniently reach many subjects.

    Exploratory data analysis refers to a variety of practices that researchers use to reduce a great many variables to a small number overarching factors. In Peirce’s three modes of inference, exploratory data analysis corresponds to abduction.Meta-analysis is the technique research psychologists use to integrate results from many studies of the same variables and arriving at a grand average of the findings.

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    A History Of Experimental Psychology

    Questions about the nature of human behavior and the connection of the body and mind go back to classic philosophers like Plato and Aristotle. Likewise, the debate over nature vs nurture raged long before experimental psychology came along in its formal and modern form.

    But the centuries of philosophizing about why people behave in the manners in which they behave sparked the interest of scientific researchers to study human behavior in an empirical manner. If the principles of the scientific method could be used for the study of behavior, perhaps scientists could provide definitive answers to the age-old questions surrounding human behavior.

    Thus, experimental psychology was born.

    The first experimental psychology lab in the world was founded in Leipzig, Germany, in 1879 by Wilhelm Wundt. There, Wundt primarily studied feelings and sensations in a structured manner using objective, systematized measures and controls.

    For example, Wundt used his background in physiology to design an experiment on sensory processes in which each participant was exposed to the same stimulus, such as the sound of a metronome. Each participant was then asked to provide a report of the sensations they experienced, a process called introspection.

    While Wundts process of introspection didnt remain a long-lasting approach to studying psychological processes, his insistence on controlling the experimental environment has had a long-term impact on how psychological research is conducted.

    So When Is A Study Not An Experiment

    Experimental Design Worksheet Answers Psychology

    A simple test would be to ask yourself:

    • Did the researchers create the groups/conditions?

    If they did, then youve got an experiment.

    • Serotonin study: the researchers chose who drank which drink and when.
    • Rat study: the researchers chose which rats to castrate and which ones not to.
    • TV study: they told which kids to watch TV and which ones not to.

    If the researchers didnt create the groups you might be better to call it a study to be on the safe side.

    In a true experiment it is the researchers who manipulate the independent variable .

    For example, in studies that compare cultures the researchers cannot create the groups because people are born into their existing cultures. These types of studies are most commonly correlational studies.

    Another example is research on communication in relationships: the researchers compare the differences between couples with positive communication with those who have negative communication, but they didnt create these groups they occurred naturally. These are also correlational studies.

    To conclude: if the researchers create the groups for comparison its an experiment. If not, youre safer to call it a study.

    Qualitative studies are never experiments, so be extra-careful when using this word in Paper 3.

    • Are they testing a causal relationship between the IV and the DV?

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    Control Groups In Experiments

    Control groups are essential to experimental design. When researchers are interested in the impact of a new treatment, they randomly divide their study participants into at least two groups:

    • The treatment group receives the treatment whose effect the researcher is interested in.
    • The control group receives either no treatment, a standard treatment whose effect is already known, or a placebo .

    The treatment is any independent variable manipulated by the experimenters, and its exact form depends on the type of research being performed. In a medical trial, it might be a new drug or therapy. In public policy studies, it could be a new social policy that some receive and not others.

    In a well-designed experiment, all variables apart from the treatment should be kept constant between the two groups. This means researchers can correctly measure the entire effect of the treatment without interference from confounding variables.

    • You pay the students in the treatment group for achieving high grades.
    • Students in the control group do not receive any money.

    Studies can also include more than one treatment or control group. Researchers might want to examine the impact of multiple treatments at once, or compare a new treatment to several alternatives currently available.

    • The treatment group gets the new pill.
    • Control group 1 gets an identical-looking sugar pill
    • Control group 2 gets a pill already approved to treat high blood pressure

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