That's because a lot of VoIP services out there go by their product names and don't make a lot of noise about it. (That's not a big deal and they're not trying to hide it. For example, if you've heard of Skype, you've heard of one of the best-known Web-based VoIP services in use.
The Range Rule. The range rule tells us that the standard deviation of a sample is approximately equal to one fourth of the range of the data. In other words s = (Maximum â Minimum)/4.This is a very straightforward formula to use, and should only be used as a very rough estimate of the standard deviation.he Range Rule. The range rule tells us that the standard deviation of a sample is approximately equal to one fourth of the range of the data. In other words s = (Maximum â Minimum)/4.
MATLAB's std function will return the standard deviation of a distribution, so we just have to divide this by the square root of the sample size to get the standard error of the mean (SEM). 1  data=randn(1,30); sem=std(data)/sqrt(length(data)) % standard error of the mean sem = 0.1813.