 Hello and welcome to this session. In this session, we will discuss about the concept of Six Sigma. Now, this concept is used by companies in showing that 99.997% of their products are non-effective and are according to the customer's expectations. The 99.997% is decided using the normal distribution. Let us understand it with the help of an illustration. Suppose a company produces 50,000 bags of diameter 2 inches. Now, the manufacturer wants to know whether the bags produced by his company are according to the specified measurements or not. He decides if the production is according to the given specifications, then he will accept the loss produced, otherwise he will reject the loss. Now, the question arises, how will he decide whether to accept it or reject it? First, he uses the statistical method. He selects randomly a sample of 50 bags then he measures the diameter of each bag in the sample and notes down the details. Now, since he was specified that the bags should be of diameter 2 inches, that the size of bags should be 2 inches, that he finds that most of the bags are not gravity of diameter 2 inches. Some of them are having diameter no than 2 inches and some are having less than 2 inches to the size of tolerance level, that is, he specifies the limits of the diameter. He decides that the size of bags should not exceed 2.06 inches and should not be less than 1.94 inches. 99.997% of bags lie within the given limits. He will accept the loss, otherwise he will reject the loss. Now, he constructs a risk of loss for the recorded mediums which gives a normal distribution. Now, minimum of the sample is equal to 2 and let the standard deviation be 0.01. So, this is the normal curve with mean 2 and standard deviation sigma is equal to 0.01. Now, here on right side of the mean, we have marked the values as x bar plus sigma, x bar plus 2 sigma, x bar plus 3 sigma, x bar plus 4 sigma, x bar plus 5 sigma and x bar plus 6 sigma. Similarly, on left side of the mean, we have marked the value as x bar minus sigma, x bar minus 2 sigma, x bar minus 3 sigma, x bar minus 4 sigma, x bar minus 5 sigma then x bar minus 6 sigma. So, here 1.94 is the minimum value and 2.06 is the maximum value. Now, if 68% bags are within the limit then the level is 2 sigma. If 99.4% bags are within the limit then the level is 4 sigma. And if 99.997% bags are within the limit then the level is 6 sigma. Now, see x bar plus 6 sigma gives upper limit decided by the manufacturer that is 2.06 and x bar minus 6 sigma gives lower limit that is 1.94. From the graph, we see that most of the values are within the required limits and very few values are outside the required limit. So, he accepts the lot of 15,000 bags produced by the company. So, this is the basic concept of 6 sigma and this completes our session. Hope you all have enjoyed the session.