When a compressor pumps one CFM (cubic foot per minute), that means the intake port inhales one cubic foot of free air (air at atmospheric pressure, which is 0 psig) per minute. (Note: A CFM does not mean in any sense the compressed volume.) So the unit really measures the mass of air flowing per minute, not volume per minute, since a cubic foot of free air is a unit of mass.
This second scale has a mean and standard deviation that have been arbitrarily set. A z score, for example, is a raw score that has been transformed to a scale with a mean of 0 and a standard deviation of 1.
And here they are graphically: You can calculate the rest of the z-scores yourself! Here is the formula for z-score that we have been using: 1  z is the z-score (Standard Score). 2  x is the value to be standardized. 3  Î¼ is the mean. 4  Ï is the standard deviation.ou can calculate the rest of the z-scores yourself! Here is the formula for z-score that we have been using: 1  z is the z-score (Standard Score). 2  x is the value to be standardized. 3  Î¼ is the mean.