The Cpk value seems not correct for the one-sided specification when using the function of CapabilityAnaylsis

[KEWH4E]

For example, when setting LSL=NULL as below, the calculated Cpk is 7.39. However, the correct Cpk should be 2.46. Could the author help to review the code?

CapabilityAnaylsis <-
ggplot(Process_Data, aes(x = Value)) + #init ggplot
geom_histogram(binwidth = .75, color="purple") + #make the histogram
stat_QC_Capability(
LSL=NULL, USL=37, #Specify LSL and USL
show.cap.summary = c("Cp", "Cpk", "Pp, "Ppk"), #selected summary
digits = 2, #report two digits
method="XmR") + #Use the XmR method
scale_x_continuous(expand = expand_scale(mult = c(0.15,.65))) #pad the X-axis
CapabilityAnaylsis

[KEWH4E]

@kenithgrey Thanks