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.
Save. DAJ/amana images/Getty Images. A Z score is a statistical calculation that you can perform on a single data point that belongs to larger data set. The Z score tells you how far -- in standard deviations -- that data point is from the mean, or average, of the data set.ave. DAJ/amana images/Getty Images. A Z score is a statistical calculation that you can perform on a single data point that belongs to larger data set. The Z score tells you how far -- in standard deviations -- that data point is from the mean, or average, of the data set.