A correlation coefficient is a numerical index that reflects the relationship between two variables.
The correlation coefficient helps us to know how strong is the relation between two variables. Its value is always between +1 to -1, where, the numerical value shows how strong is the relation between them and, the '+' or '-' sign shows whether the relationship is positive or negative.
The given blank in the sentence can be filled with two variables.
Hence, A correlation coefficient is a numerical index that reflects the relationship between two variables.
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