Research Variables – Dependent and Independent Variables

Research is the foundation of any science, including both hard sciences such as physics, chemistry and the social sciences such as psychology, management and education. The steps and process involved in the research can vary depending on the type of research being done and the hypothesis being tested. Research methods such as Naturalistic observation and surveys are often less structured, where as experimental methods are more structured. Depending upon what is observed or experienced, new theories are developed. There are aspects of a theory or aspects of a study that can change or vary as part of interaction within the theory, defined as variables. Variables are anything that can change of effect the results of a study. In an experimental method, the experiment is conducted by changing the value of one variable and measuring the changes in another variable while holding or assuming surroundings constant. There is no limit to the number of variables that can be measured, although the more variables, the more complex the study and the more complex the statistical analysis.

Research Variables - Dependent and Independent Variables

Every experiment has at least two types of variables: an independent and dependent. An independent variable is the variable that the researchers systematically  manipulate in the experiment. An independent variable is measured, manipulated, or selected by the experimenter to determine its relationship to an observed phenomenon. This might be a variable that you control, like a treatment, or a variable not under your control, like an exposure. It also might represent a demographic factor like age or gender. While the independent variable is often manipulated by the researcher, it can also be a classification where subjects are assigned to groups. In a study where one variable causes the other, the independent variable is the cause. In a study where groups are being compared, the independent variable is the group classification. In a research to demonstrate the increasing alcohol consumption during pregnancy actually causes a reduction in birth weight, researchers randomly assigned 50 pregnant rat either to an experimental group or to a control group. The 25 rats in the experimental group had bottles filled in with mixture of pure water and alcohol, 25 rats in the control group had bottles with water. Other than this, researchers treated all rats as much alike as possible. Aim was to have the two groups differ systematically along only one variable: alcohol versus pure water. This is independent variable; idea was to manipulate this variable independently of other factors such as diet that might affect pregnancy. In this example, birth weight is the dependent variable that is it represents the outcome that we measure, an outcome that is dependent on the manipulation of the independent variable. With experiments, then, researchers systematically manipulate the independent variable to determine if it causes a difference in the dependent variable. There are three ways to manipulate independent variables: presence or absence technique, amount technique and type technique. In presence or absence technique, the independent variable can be manipulated can be manipulated by presenting a condition or treatment to one group of individuals and withholding the condition or treatment from another group of individuals. In amount technique, the independent variable can be manipulated by varying the amount of a condition or variable such as the amount of a drug which is given to children within a learning disorder. In type technique, the independent variable is to vary the type of the condition or treatment administered.

In an experiment, a dependent variable is the factor which is observed and measured to determine the effect of the independent variable, that is, that factor that appears, disappears, or varies as the experimenter introduces, removes, or varies the independent variable. The dependent variable is the participant’s response. The dependent variable is the outcome of experiment. In an experiment, it may be what was caused of what changed as a result of the study, in a comparison of groups; it is what they differ on. In research study on rats, described in previous paragraph, the experimental group is exposed to alcohol, and the control group is not. If we observe that the rat pups in the groups differ reliably in birth weight, and then we can conclude alcohol exposure caused this difference. In this example birth weight is a dependent variable.

In an experiment, the independent variable is the variable that is varied or manipulated by the researcher, and the dependent variable is the response that is measured. An independent variable is the presumed cause, whereas the dependent variable is the presumed effect. The independent variable is the antecedent, whereas the dependent variable is the consequent. In experiments, the independent variable is the variable that is controlled and manipulated by the experimenter; whereas the dependent variable is not manipulated, instead the dependent variable is observed or measured for variation as a presumed result of the variation in the dependent variable. Dependent variables can be influence by controlled variables.

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