what is a good z score 
the higher or lower a z score is the further away from the mean the point is this isn t necessarily good or bad it merely shows where the data lies in a normally distributed sample this means it comes down to preference when evaluating an investment or opportunity for example some investors use a z score range of 3 0 to 3 0 because 99 7 of normally distributed data falls in this range while others might use 1 5 to 1 5 because they prefer scores closer to the mean 