mqr.spc.XBarParams.

from_range

static XBarParams.from_range(centre, r_bar, nobs, nsigma=3)

Constructs XBarParams from an average range.

Using sample range to estimate process standard deviation can be inefficient. See Efficieny of estimates of process standard deviation.

Parameters:

centrefloat

Process target mean.

r_barfloat

Average sample range from a reference in-control process.

nobsint

Size (fixed) of samples used to calculate (r_bar).

nsigmafloat

Number of stderr to set control limits.