The process is in a state of control both before and after the intervention (periods 1 & 2). However, the proportion of dropped calls before the intervention (period 1) was 14.09%, and after the intervention (period 2) is 22.12%. As the charts show, the average dropped calls actually increased. It looks like the improvement oriented activities yielded no positive results.

Statistical Process Control is required for determining Capability indices, which are indicators of risk. In this case, as this condition is met, we can assess process capability using the equivalent value for Cpk (capability of a process to produce within specifications) before the intervention (period 1 = 0.3588), and after the intervention (period 2 = 0.2560). Conclusions: The process is neither capable in period 1 nor in period 2 (Cpk < 1). Not only did the intervention not result in any improvement in performance, but the process variability increased considerably after the implementation of the improvement oriented activities.

[1] 0.1409

[1] 0.2212

[1] 0.3587615

[1] 0.2560489