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.
The coefficient of variation (CV) refers to a statistical measure of the distribution of data points in a data series around the mean.It represents the ratio of the standard deviation to the mean.alculating the coefficient of variation. The main steps involved in computation of coefficient of variation are: 1. Compute the sample mean, using the formula Î¼ = 'x i / n, where n indicates the number of data point x i in the sample, and the total is over all values of i. The term i is read as a subscript of x. 2.