In statistics, a confounding variable (also confounding factor, hidden variable, lurking variable, a confound, or confounder) is an extraneous variable in a statistical model that correlates (positively or negatively) with both the dependent variable and the independent variable. Such a relation between two observed variables is termed a spurious relationship. In the case of risk assessments evaluating the magnitude and nature of risk to human health, it is important to control for confounding to isolate the effect of a particular hazard such as a food additive, pesticide, or new drug. For prospective studies, it is difficult to recruit and screen for volunteers with the same background (age, diet, education, geography, etc.), and in historical studies, there can be similar variability. Due to the inability to control for variability of volunteers and human studies, confounding is a particular challenge. For these reasons, experiments offer a way to avoid most forms of confounding.

As an example, suppose that there is a statistical relationship between ice cream consumption and number of drowning deaths for a given period. These two variables have a positive correlation with each other. An evaluator might attempt to explain this correlation by inferring a causal relationship between the two variables (either that ice cream causes drowning, or that drowning causes ice cream consumption). However, a more likely explanation is that the relationship between ice cream consumption and drowning is spurious and that a third variable (the season) causes both variables to increase: during the summer, warmer temperatures lead to increased ice cream consumption as well as more people swimming and thus more drowning deaths.

Read more about Confounding:  Types of Confounding, Examples, Decreasing The Potential For Confounding To Occur

Other articles related to "confounding":

Abortion–breast Cancer Hypothesis - Epidemiological Studies - Confounding Factors
... There are many confounding factors for breast cancer ... All of these confounding factors have an effect, directly or indirectly, on hormones which impact breast cancer risk, but they do not significantly affect the ...
Decreasing The Potential For Confounding To Occur
... A reduction in the potential for the occurrence and effect of confounding factors can be obtained by increasing the types and numbers of comparisons performed in an analysis ... among different subgroups of analyzed units, confounding may be less likely ... Peer review is a process that can assist in reducing instances of confounding, either before study implementation or after analysis has occurred ...
Design Of Quasi-experiments - Disadvantages
... of impact are subject to contamination by confounding variables ... This deficiency in randomization makes it harder to rule out confounding variables and introduces new threats to internal validity ... of causal relationships are difficult to determine due to a variety of extraneous and confounding variables that exist in a social environment ...
Science Experiments - Contrast With Observational Study
... to fit a physical or social system into a laboratory setting, to completely control confounding factors, or to apply random assignment ... It can also be used when confounding factors are either limited or known well enough to analyze the data in light of them (though this may be rare when social phenomena are under examination) ... In order for an observational science to be valid, confounding factors must be known and accounted for ...
Threats To Internal Validity - Confounding
... A major threat to the validity of causal inferences is confounding Changes in the dependent variable may rather be attributed to the existence or variations in the degree of a third variable ...

Famous quotes containing the word confounding:

    Murder in the murderer is no such ruinous thought as poets and romancers will have it; it does not unsettle him, or fright him from his ordinary notice of trifles: it is an act quite easy to be contemplated, but in its sequel, it turns out to be a horrible jangle and confounding of all relations.
    Ralph Waldo Emerson (1803–1882)