After implementing process improvement actions, new data placed on the SPC chart of the old process shows consistent variability about the mean on the X-bar chart, but the R chart shows eight points below the R-bar line. What is happening? A The improvement actions were successful in shifting the process mean. B The R-bar chart is now in control. C The process is exhibiting less variability between observations (part to part). D The R-bar chart is out-of-control, indicating that the improvement action was not effective