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.
1 Click the Calculate button to view the results. 2  The output will consist of a table containing the sample mean difference (Sample Mean), the standard error of the difference in sample means (Std. 3  Err.), the degrees of freedom (DF), the T statistic (T-stat) and the P-value for the test. Enter a value for the number of trials in the first sample. 2  Enter a value for the number of successes in the second sample. 3  Enter a value for the number of trials in the second sample. 4  Click the Next button to select between a hypothesis test and confidence interval computation.