The inventory supply clerk notices that the IV tubing is not always exactly the same length, so she measures three pieces of tubing at random out of 7 lots of tubing. Assuming that is enough data to create X-bar and R -charts, she determines the sample means are 22.7, 22.5, 21.9, 21.3, 22.1, 22.3, 21.2, and the sample ranges are: 0.3, 0.2, 0.4, 0.2, 0.3, 0.2, and 0.5.

What is the upper control limit for X-Bar-Chart?

choices:

22

21.69

22.31

20.45