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Association (statistics)

 

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Association (statistics)



 
 
In statistics
Statistics

Statistics is a Mathematics pertaining to the collection, analysis, interpretation or explanation, and presentation of data. It also provides tools for prediction and forecasting based on data....
, an association comes from two variables that are related and is often confused with causality
Causality

Causality denotes a necessary relationship between one event and another event which is the direct consequence of the first.While this informal understanding suffices in everyday use, the Philosophy analysis of how best to characterize causality extends over millennia....
 though association does not imply a causal relationship. In formal statistics, correlation
Correlation

In probability theory and statistics, correlation indicates the strength and direction of a linear relationship between two random variables....
 and association are related but not entirely overlapping concepts.

For example, the United Nations
United Nations

The United Nations is an international organization whose stated aims are to facilitate cooperation in international law, international security, economic development, Social change, human rights and achieving world peace....
 studied governmental failure—when governments fall or are overthrown and found that the best indicator of a government about to fall was the infant mortality rate.






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In statistics
Statistics

Statistics is a Mathematics pertaining to the collection, analysis, interpretation or explanation, and presentation of data. It also provides tools for prediction and forecasting based on data....
, an association comes from two variables that are related and is often confused with causality
Causality

Causality denotes a necessary relationship between one event and another event which is the direct consequence of the first.While this informal understanding suffices in everyday use, the Philosophy analysis of how best to characterize causality extends over millennia....
 though association does not imply a causal relationship. In formal statistics, correlation
Correlation

In probability theory and statistics, correlation indicates the strength and direction of a linear relationship between two random variables....
 and association are related but not entirely overlapping concepts.

For example, the United Nations
United Nations

The United Nations is an international organization whose stated aims are to facilitate cooperation in international law, international security, economic development, Social change, human rights and achieving world peace....
 studied governmental failure—when governments fall or are overthrown and found that the best indicator of a government about to fall was the infant mortality rate. Causally, it may seem as though the dying children cause the government to fall but their mere association does not imply this.

Another example is the rates of ice cream
Ice cream

Ice cream or ice-cream is a frozen dessert usually made from dairy products, such as milk and cream, combined with fruits or other ingredients....
 consumption and murder
Murder

Murder as defined in common law countries, is the unlawful killing of another human being with intent , and generally this state of mind distinguishes murder from other forms of unlawful homicide....
, which exhibit a strong positive association. Which causes which; does eating ice cream cause murder or does murder make people eat ice cream? The answer is neither—increases in both ice cream consumption and murder are associated with hot weather.

Another perspective on the relationship between association and causality is that association does not imply a direct causal connection between the associated variables. If, however, association is nonrandom (i.e., not due purely to chance), then it implies that some causal mechanism is operative. Often, the nature of the causal mechanism underlying an association is the joint influence of one or more common causes operating on the variables in question. For example, both the increase in ice cream consumption and murder may occur during warm weather (a conclusion that would require further information to confirm or fail to confirm). If this were so, then the occurrence of the association between ice cream consumption and murder would be a manifestation of causation, but not in the simple, linear fashion that one initially might be tempted to assume. Associations of this sort, involving a third variable that jointly causes the association between the two original variables, is often termed "spurious association."

Several tests can be used to determine association. Computation of any of several versions of the correlation
Correlation

In probability theory and statistics, correlation indicates the strength and direction of a linear relationship between two random variables....
 coefficient, the P test, t-test
Student's t-test

A t-test is any statistical hypothesis testing in which the test statistic has a Student's t-distribution if the null hypothesis is true. It is applied when the population is assumed to be normal distribution but the sample sizes are small enough that the statistic on which inference is based is not normally distributed because it relies...
, and chi-squared test are the most common.

See also

  • Correlation does not imply causation