Correlation: Definition and Examples


Correlation is a statistical term that tends to explain nature and degree of the relationship between variables. The nature of relationship may be either positive or negative depending on how the variables move. The degree of relationship is measured by how closely the variables are correlated, which may either strong or weak. Although relationship between variables may be as a result of cause and effect, correlation may not necessarily imply causation.

Positive correlation

A positive correlation may be demonstrated by the relationship between smoking and incidences of lung cancer. An analysis of the cause of lung cancer may strongly be linked to the fact that the patient has been a regular smoker. In fact, American Cancer Society (2009) describes smoking as the major cause of lung cancer deaths in United States. Although there are other factors that may cause lung cancer, statistics reveal that the rise of lung cancer cases directly correspond to the rise in smoking. Therefore, smoking is being viewed as direct cause of lung cancer, meaning that there is a positive correlation between the two variables.

The strength of relationship varies depending on how the variables are interconnected. For example, the relationship between crime and poverty has been regarded as strongly correlated (Williams 2009). William (2009) claims that people living below the poverty line are more likely to commit poverty crimes like burglary and theft and consequently end up in jail. In this case, poverty is said to be a direct causation of crime and the relationship is quite strong.

However, scholars have had controversial theories of correlation between poverty and crime with some suggesting that there are areas where poverty is quite high yet crime rate is very low (Williams 2009).

Correlation between some variables may be negative meaning that, advancement in one variable affects another variable adversely. For example, alcohol consumption usually causes poor performance, both in education and work as it affects the human memory (Verster et al 2002). When one consumes a lot of alcohol, the aftermath is hangover which is associated with problems like sleepiness, drowsiness, and low concentration leading to poor memory functioning and consequently poor performance. This implies that as alcohol consumption increase, performance declines thus a negative correlation between the two. Therefore alcohol consumption is a causation of negative performance.

High correlation may not necessarily mean there has been causation between the variable as the effects may be as a result of sheer coincidence. For example, a highly educated person may be earning highly at the age of 40 years (Johnston 2009). However this does not necessarily mean that the spending long time in education has resulted to high income. Although the two are highly correlated, the causation of high income may be quite different such as exerting more effort at work or favorable business environment. Therefore, a high correlation does not necessarily imply causation although the reverse is true.

Correlation between level of air pollution and the number of motor vehicles may be directly correlated (traffic pollution 2009). Although efficiency of engine performance has been enhanced leading to less fume emission, the number of motor vehicles is increasing thus increasing the emission of fumes to the air. This implies that air pollution will always be there as long as vehicles are on the road implying that presence motor vehicle is a causation of air pollution.

Work cited

American Cancer Society. “Tobacco-Related Concerns Fact Sheet”. Tobacco-Related Cancers Fact Sheet. 2009. Web.

Johnson, Ian. I’ll Give You a Definite Maybe: An Introductory Handbook on Probability, Statistics, and Excel. 2009. Web.

Traffic pollution – measuring the real damage”. Traffic pollution – measuring the real damage. 2009. Web.

Williams Joseph. “Poverty and Crime” Christian Association for Prison Aftercare. 2009. Web.

Verster et al. Alcohol Hangover Effects on Memory Functioning and Vigilance Performance after an Evening of Binge Drinking. 2002. Web.

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