The Difference Between Control Group and Experimental Group

The Difference Between Control Group and Experimental Group In an experiment, data from an experimental group is compared with data from a control group. These two groups should be identical in every respect except one: The difference between a control group and an experimental group is that the independent variable is changed for the experimental group, but is held constant in the control group. Key Takeaways: Control vs. Experimental Group The control group and experimental group are compared against each other in an experiment. The only difference between the two groups is that the independent variable is changed in the experimental group. The independent variable is controlled or held constant in the control group.A single experiment may include multiple experimental groups, which may all be compared against the control group.The purpose of having a control is to rule out other factors which may influence the results of an experiment. Not all experiments include a control group, but those that do are called controlled experiments.A placebo may also be used in an experiment. A placebo isnt a substitute for a control group because subjects exposed to a placebo may experience effects from the belief they are being tested. What Are Groups in Experiment Design? An experimental group is the group that receives an experimental procedure or a test sample. This group is exposed to changes in the independent variable being tested. The values of the independent variable and the result 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 variables 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. 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 (the most common component of air) or deoxygenated air (which likely contained extra carbon dioxide). Which container is the control? Which is the experimental group? Control Groups and Placebos The most common type of control group is one held at ordinary conditions so it doesnt experience a changing variable. For example, If you want to explore the effect of salt on plant growth, the control group would be a set of plants not exposed to salt, while the experimental group would receive the salt treatment. If you want to test whether the duration of light exposure affects fish reproduction, the control group would be exposed to a normal number of hours of light, while the duration would change for the experimental group. Experiments involving human subjects can be much more complex. If youre testing whether a drug is effective or not, for example, members of a control group may expect they will not unaffected. To prevent skewing the results, a placebo may be used. A placebo is a substance that doesnt contain an active therapeutic agent. If a control group takes a placebo, participants dont know whether they are being treated or not, so they have the same expectations as members of the experimental group. However, there is also the placebo effect to consider. Here, the recipient of the placebo experiences an effect or improvement because she believes there should be an effect. Another concern with a placebo is that its not always easy to formulate one that truly free of active ingredients. For example, if a sugar pill is given as a placebo, theres a chance the sugar will affect the outcome of the experiment. Positive and Negative Controls 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. Sources Bailey, R. A. (2008). Design of Comparative Experiments. Cambridge University Press. ISBN 978-0-521-68357-9.Chaplin, S. (2006). The placebo response: an important part of treatment. Prescriber: 16–22. doi:10.1002/psb.344Hinkelmann, Klaus; Kempthorne, Oscar (2008). Design and Analysis of Experiments, Volume I: Introduction to Experimental Design (2nd ed.). Wiley. ISBN 978-0-471-72756-9.

Author, Sociologist, and Activist W.E.B. Du Bois

Author, Sociologist, and Activist W.E.B. Du Bois W.E.B. Du Bois was born in Great Barrington, Massachusetts. At the time, Du Bois’s family was one of the few black families living in the predominantly Anglo-American town. While in high school, Du Bois showed a big concern for the development of his race. At fifteen years of age, he became the local correspondent for the New York Globe and gave lectures and wrote editorials spreading his ideas that black people needed to politicize themselves. Fast Facts: W.E.B. Du Bois Full Name: William Edward Burghardt (W.E.B. for short) Du BoisBorn: February 23, 1868 in Great Barrington, MADied: August 27, 1963Education: Bachelors from Fisk University and Harvard University, Masters from Harvard. First Black to earn a doctorate degree at Harvard.Known For: Editor, writer, and political activist. As the first person to use a scientific approach to study social phenomenon, Du Bois is often called the Father of Social Science.Key Accomplishments: Played a leading role in the struggle for black civil rights in the United States. Founded and led the National Association for the Advancement of Colored People (NAACP) in 1909.Publications: The Philadelphia Negro (1896), Souls of Black Folks (1903), The Negro (1915), The Gift of Black Folk (1924), Black Reconstruction (1935), The Color of Democracy (1945) Education In 1888, Du Bois earned a degree from Fisk University in Nashville Tennessee. During his three years there, Du Bois’ knowledge of the race problem became more definite and he became determined to help expedite the emancipation of black people. After graduating from Fisk, he entered Harvard on scholarships. He earned his bachelor’s degree in 1890 and immediately began working towards his master’s and doctorate degree. In 1895, Du Bois became the first African-American to earn a doctorate degree at Harvard University. Career and Later Life After graduating from Harvard, Du Bois took a teaching job at Wilberforce University in Ohio. Two years later he accepted a fellowship at the University of Pennsylvania to conduct a research project in Philadelphia’s seventh ward slums, which allowed him to study blacks as a social system. He was determined to learn as much as he could in an attempt to find the â€Å"cure† for prejudice and discrimination. His investigation, statistical measurements, and sociological interpretation of this endeavor was published as The Philadelphia Negro. This was the first time such a scientific approach to studying social phenomenon was undertaken, which is why Du Bois is often called the Father of Social Science. Du Bois then accepted a teaching position at Atlanta University. He was there for thirteen years during which he studied and wrote about morality, urbanization, business and education, the church, and crime as it affected Black society. His main goal was to encourage and help social reform. Du Bois became a very prominent intellectual leader and civil rights activist, earning the label â€Å"The Father of Pan-Africanism.† In 1909, Du Bois and other like-minded supporters founded the National Association for the Advancement of Colored People (NAACP). In 1910, he left Atlanta University to work full-time as the Publications Director at the NAACP. For 25 years, Du Bois served as the editor-in-chief of the NAACP publication The Crisis. By the 1930s, the NAACP had become increasingly institutionalized while Du Bois had become more radical, which led to disagreements between Du Bois and some of the other leaders. In 1934 he left the magazine and returned to teaching at Atlanta University. Du Bois was one of a number of African-American leaders investigated by the FBI, which claimed that in 1942 his writings indicated him to be a socialist. At the time Du Bois was chairman of the Peace Information Center and was one of the signers of the Stockholm Peace Pledge, which opposed the use of nuclear weapons. In 1961, Du Bois moved to Ghana as an expatriate from the United States and joined the Communist Party. In the final months of his life, he renounced his American citizenship and become a citizen of Ghana.