To co relate is to measure the relationship between two variables.
Measured variables are called CO VARIABLES.
Correlation may be negative or positive. However it is not a measure of CAUSE AND EFFECT. There is only an association between two variables.
POSITIVE CORRELATION means as variable increases, the other increases also.
NEGATIVE CORRELATION means as one variable increases, the co variable decreases. DILALLA 1988 found a negative correlation between those who stayed longer in day care.