The PEARSON function returns the Pearsonproduct moment correlation coefficient, r, a dimensionless index that ranges from 1.0 to 1.0 inclusive and reflects the extent of a linear relationship between two data sets.
Syntax
=PEARSON(array1,array2)
Arguments
Argument  Description 

array1  A range of cells containing a set of independent variables 
array2  A range of cells containinga set of dependent variables 
Note: The PEARSON function is the same as the CORREL function – both functions should produce the same results.
Examples
A  B  C  D  E  F  

1  Array1  Array2  Formula  Result  Notes  
2  3  8  =PEARSON(A2:A6,B2:B6)  0.83205  Correlation coefficient of the two data sets in columns A and B  
3  2  7  
4  5  10  
5  4  14  
6  6  18 
Usage note: Use the correlation coefficient to determine the relationship between two properties. For example, you can examine the relationship between a location’s average temperature and the use of air conditioners.
Common Function Error(s)
Problem  What went wrong  

#N/A  Occurs if the supplied array arguments have different lengths  
#DIV/0!  Occurs if:

The Pearson productmoment correlation coefficient is a statistical measurement of the correlation, linear association, between two sets of values, x and y.
The equation for the correlation coefficient is:
where and are the sample means AVERAGE(array1) and AVERAGE(array2).
If the value of r is close to +1, this indicates a strong positive correlation, and if r is close to 1, this indicates a strong negative correlation.
See Wikipedia for more information on the Pearson ProductMoment Correlation Coefficient.