correlation

in education, a statistical term for the degree to which two or more entities show a tendency to vary together. The relationship may be a positive one ( as one rises/falls so does the other ) or a negative one ( as one rises, the other falls, and vice versa). For example, there may be a negative correlation found between levels of social deprivation and examination success and a positive correlation between levels of truancy and daytime juvenile crime. It is important to note that correlation does not necessarily establish a causal relationship: although x and y may vary together, one cannot therefore claim that x causes y or that y causes x. A common example given is the positive correlation of ice cream sales and the incidence of accidental deaths by drowning. One does not cause the other: instead, the key variable is sunny weather which affects both.