Struct XBarSChart 

pub struct XBarSChart { /* private fields */ }

X-bar and Standard Deviation (X-bar-S) control chart.

Monitors the process mean (X-bar chart) and process variability (S chart) using subgroup standard deviations. Preferred over X-bar-R for larger subgroups where range is a less efficient estimator.

Algorithm

1. For each subgroup, compute the mean (X-bar) and sample standard deviation (S).
2. Compute the grand mean (X-double-bar) and average S (S-bar).
3. X-bar chart limits: CL = X-double-bar, UCL/LCL = CL +/- A3 * S-bar.
4. S chart limits: CL = S-bar, UCL = B4 * S-bar, LCL = B3 * S-bar.

Reference

Montgomery, D.C. (2019). Introduction to Statistical Quality Control, 8th ed., Chapter 6: Control Charts for Variables.

Implementations

impl XBarSChart

pub fn new(subgroup_size: usize) -> Self

Create a new X-bar-S chart with the given subgroup size.

Panics

Panics if subgroup_size is not in the range 2..=10.

pub fn s_limits(&self) -> Option<ControlLimits>

Get the S chart control limits, or None if insufficient data.

pub fn s_points(&self) -> &[ChartPoint]

Get the S chart points.

Trait Implementations

impl ControlChart for XBarSChart

fn add_sample(&mut self, sample: &[f64])

Add a subgroup sample. The sample length must equal the chart’s subgroup size.

fn control_limits(&self) -> Option<ControlLimits>

Get the computed control limits, or None if insufficient data.

fn is_in_control(&self) -> bool

Check if the process is in statistical control.

fn violations(&self) -> Vec<Violation>

Get all violations detected across all chart points.

fn points(&self) -> &[ChartPoint]

Get all chart points.