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.
Use the following format to find a z-score: z = X - Î¼ / Ï. This formula allows you to calculate a z-score for any data point in your sample. 1  Remember, a z-score is a measure of how many standard deviations a data point is away from the mean.2  In the formula X represents the figure you want to examine.his will start out the calculations for a z-score. 1  For example, in our sample of tree heights we want to find out how many standard deviations 7.5 is from the mean of 7.9. 2  Therefore, you would perform the following: 7.5 - 7.9.