What is the difference between lowercase sigma and lowercase sigma squared? Lowercase sigma is used for the population standard deviation while the letter s is used for the sample standard deviation. If I wanted to add up the numbers above, I would use the following format of sigma:Īssuming the data set was the population data, I would use the following format of sigma for calculating the population standard deviation:įrequently Asked Questions (FAQ) about sigma What is the symbol used for the sample standard deviation? Here are a few examples of how sigma can be used in statistical calculations. Below is a graphic of the Empirical Rule.Įmpirical Rule An industry example of sigma When adding and subtracting various numbers of standard deviations from the mean, you will encompass different percentages of the total data set. Īnother use of lowercase sigma is in the Empirical Rule, which describes the distribution of data in a normal distribution. This capability is defined as having only 3.4 defects per one million opportunities often referred to as 3.4 parts per million (ppm). In this case, it is a measure of process capability The term Six Sigma means that the closest specification of a process or product is six standard deviations away from the mean of a normally distributed set of data. Lowercase sigma is also referred to in the context of Six Sigma. Interestingly, the formula for the standard deviation includes the uppercase notation of sigma. When used in the uppercase, it indicates a summation of values as shown below:Ī lowercase sigma signifies and represents the population standard deviation of a set of quantitative data. Overview: What is sigma?īelow are the uppercase and lowercase symbols for sigma: The uppercase use of sigma denotes a summation while the lowercase represents a measure of variation. The meaning of sigma in statistics is a function of whether you use the upper or lower case of the letter.
0 kommentar(er)
