TOPIC: six sigma in relation to process duration

Would it be possible to elaborate on the relation between six sigma quality requirement and process duration?

The question has 13 days of the PERT task duration estimate and 1 day as a standard deviation. The correct answer reads that the task can be completed in 7 to 19 days period. I don't really understand where 6 days duration deviation came from...

Any input is greatly appreciated.

I don't want to confuse you further nor give you a wrong answer that is interpreted as the book answer. With that disclaimer, I want to offer what I think the explanation to the apparent question is trying to say.

When you look at an average and then the standard deviation, you normally look at the range of possibilities within the 3 standard deviations from the average on either side.

So, if your SD is 1, then 3 to left and 3 to right makes 6. I think the total deviation from left to right has something to do with answer you received.

I understand your question, but I don't want to take any further guesses as to the explanation. Hopefully you can provide the source of the question, and maybe someone else has seen this question, or better yet, has a good explanation.