You have just used the capability index $($Cpk$)$ formulas to compute the two values "min $[1\mathrm{.}5,1]."$ Which of the following is the proper interpretation of these numbers?

The true capability index value is $1.$

The mean of the production process has shifted to the left of the design limits$.$

The mean of the production process has shifted to the right of the design limits$.$

The mean has not shifted at all.

The true capability index value is between $1\mathrm{.}5$ and $1.$