Definition of Correlation

According  to prof, king correlation means that between two series or group  of data  there  exists  some casual connection  prof, king  has also  explained,  If it is proved true that in a large number of instances two variables tend always to fluctuate in the same or in opposite direction, we  consider that the fact  is established that a relationship  exists. This relationship is called correlation.

According to Boddington, Whenever  some definite connections exist between the two or more group. Classes or series of data, there is said to be correlation.

E . Davenport has expressed his views as, the whole subject of correlation refers to the inter relation between separate character by which they tend in some degree, at least, to move together. Thus two or more variables are said to be correlated if the change in one variable result or associated with a corresponding changes in other variable.