A Six sigma table is a table that depicts the (six) sigma value corresponding to various accuracy levels. The six sigma table can be downloaded here. By looking down the tabulated values of the accuracy levels, you can find the (six) sigma level that corresponds to your accuracy level.
The sigma table has five columns – the yield or the accuracy level ( 1 – the defect rate), the defect rate, the sigma level corresponding to that accuracy level, the defects per million opportunities and the grade that can be assigned to a project depending on its sigma level. The yield level in the table is actually the number of correct parts out of 100. You can then calculate the defect level by subtracting the yield rate from 100. The DPMO or the defect per million opportunities is the number of chances that part or transaction had of going wrong per million opportunities.
The six sigma table can be used as a ready reference when you want to quickly ascertain the sigma level of a process. The table can also be used to check the improvement in sigma levels that can be achieved when a process is moved from a lower accuracy level with a lower sigma level to higher accuracy resulting in a higher sigma level. By doing a quick back of envelop calculation, you can calculate the total cost of moving from the lower accuracy level to a higher accuracy level.
The sigma table also provides the defects per million opportunities (or DPMO) that correspond to each sigma level. Suppose your process is currently running at the six sigma level. It this case, you will only have 3.4 parts or transactions going wrong, out of a million. On the other hand if your process was humming along at a 3 sigma level, you would end up with 66,800 (yes nearly sixty six thousand) erroneous parts or transactions being produced per million.
Experts say that Quality is Free. And in this case, it actually can be. Imagine that you moved form the 3 sigma level all the way up to the six sigma level on the table – you’d end up saving a tremendous amount of money and time and would have eliminated nearly 67,000 defective parts or transactions. Obviously, moving up from a lower level on the table is far more beneficial and easier than moving up further when you are already have fairly high accuracy and sigma levels. Similarly, it would require lesser effort and money to move up by the same amount from a lower level than from a higher level.
The six sigma table is designed so that it can be conveniently printed on an A4 sheet and act as a ready reckoner for a six sigma practitioner. You may also want to look at the six sigma calculator that was made in excel.