1. The standard deviation is a constant within a data set.
2. Look up the z-score for the two scores by using the z-table backwards (read the percentile rank and figure out the z. (.05 and .44)
3. Determine the difference in z-scores between the two scores of interest. (.39)
4. Since the target scores are 2 apart, the difference in z-scores represents a z change for a raw score change of 2. (change of 2 raw score = .39z)
5. Choose one of the two scores (142). It is .44z away from the mean. Now you can do this as a ratio (2/x = .39/.44). This results in 2.25. That is the number of raw score increments 142 is away from the mean.
6. So, the mean is 142 - 2.25 = 139.75
7. Now go back and plug the mean into the z formula for a raw score of 142 and solve for sd.
   .44 = (142 - 139.75)/sd
   sd = 5.11