In the U.S., doctors usually get suspicious when a PSA level is 4.0 ng/mL. But studies show that many men with levels well above 4.0 ng/mL do not have cancer. And many men with prostate cancer have PSA scores well below this level. There are a lot of ways to tweak the PSA test to try to get better results.
The Standard Deviation Formula. In this formula, x is the value of the mean, N is the sample size, and x i represents each data value from i=1 to i=N.. The â symbol indicates that you must add up the sum. (x 1 - x) 2 + (x 2 - x) 2 + (x 3 - x) 2 + (x 4 - x) 2 + (x 5 - x) 2. . . + (x N-x) 2.
BE refers to a deviation of the buffer base (BB) from normal BB, and is the amount of base in fully oxygenated blood (which is zero at pH 7.4, the normal base value of the blood); it is equal to the amount of a strong acid or base needed to bring the pH in blood to 7.4 at a pCO2 of 40 mmHgâ5.3 kPa at 37ÂºC.