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.
The z-score, also known as standard score, is a measurement used in statistics. It is the measurement of the number of standard deviations a specific number is above or below a mean. The formula to calculate z-score is. z = (x - Î¼) / Ï. where. 1  z is the z-score, 2  x is the value to be standardized,3  Î¼ is the mean of the given set of data, 4  Ï is the standard deviation of the given set of data.t is the measurement of the number of standard deviations a specific number is above or below a mean. The formula to calculate z-score is. z = (x - Î¼) / Ï. where. 1  z is the z-score, 2  x is the value to be standardized, 3  Î¼ is the mean of the given set of data,