XBarParams#
- class mqr.spc.XBarParams(centre: float, sigma: float, nsigma: float = 3, name: str = 'XBar')#
XBar (sample mean) control parameters.
Use this class to construct traditional XBar charts. In addition to construction using class attributes, XBarParams can be constructed from sample standard deviation, sample range or historical data.
- Attributes:
- centrefloat
Centreline of the process distribution.
- sigmafloat
Standard deviation of the process distribution.
- nsigmafloat, optional
Distance in standard errors of the upper and lower control limits from the centreline.
- namestr, optional
Name of the control method.
Methods
asdict()Returns a dict representation of this class.
from_data(samples[, method, nsigma])Constructs XBarParams from reference samples.
from_range(centre, r_bar, nobs[, nsigma])Constructs XBarParams from an average range.
from_stddev(centre, s_bar, nobs[, nsigma])Constructs XBarParams from an average sample stddev.
lcl(nobs)Calculates the lower control limits for samples with sizes in nobs.
se(nobs)Standard error of xbar (standard error of the mean).
statistic(samples)XBar statistic; the sample mean.
target()Expected value of the sample mean.
ucl(nobs)Calculates the upper control limits for samples with sizes in nobs.