Find the z-score and interpret it

Question

1. Find the z-score of the value 139 in a dataset with mean 111 and standard deviation 8. Interpret the z-score in terms of number of standard deviations above or below the mean.
z-score=?

The value of 139 is ? standard deviation (above or below) the mean?

 

Answer 1

z-score = (data value - mean)/(standard deviation)

 

           = (139 - 111)/8 = 28/8 = 3.5

 

139 is 3.5 standard deviations above the mean.  

 

NOTE:  If z < 0, then the value is below the mean