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.
ÏM = standard error of the mean Ï = the standard deviation of the original distribution N = the sample size âN = Root of the sample size. The standard error of the mean, also called the standard deviation of the mean, is a method used to estimate the standard deviation of a sampling distribution.To understand this, first we need to understand why a sampling distribution is required.Don't miss these related articles:tandard Error of the Estimate. A related and similar concept to standard error of the mean is the standard error of the estimate. This refers to the deviation of any estimate from the intended values. For a sample, the formula for the standard error of the estimate is given by: