What type of Control Chart? USL of 3 and a lower spec limit of 1

[2001Wingnut]

I have a process that has an USL of 3 and a lower spec limit of 1 and no set target. The process runs best at around 1.2 - 1.5. No matter how I set it up in a Xbar& R chart using nominals the cpk numbers are around .4. Is there a better way to look at this data?

 

[Bev D]

For best advice please post your data and describe the type of process you are dealing with. otherwise we are guessing. guessing can be entertaining for us but not helpful for you.