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.
Quartile Deviation. Quartile Deviation (Q. D.) is half of the difference between the first and third quartiles. Hence, it is called Semi Inter Quartile Range. In Symbols, Q. D = Q3 â Q1. Among the quartiles Q1, Q2 and Q3, the range Q3 Q1 is called inter quartile range and (Q3-Q1)/2, Semi inter-quartile range.