Struct UChart 

pub struct UChart { /* private fields */ }

Defects per unit (U) chart.

Monitors the defect rate when the area of opportunity (inspection size) varies between subgroups. Control limits are computed individually for each subgroup based on its inspection size.

Formulas

• CL = u-bar = total_defects / total_units
• UCL_i = u-bar + 3 * sqrt(u-bar / n_i)
• LCL_i = max(0, u-bar - 3 * sqrt(u-bar / n_i))

Reference

Montgomery, D.C. (2019). Introduction to Statistical Quality Control, 8th ed., Chapter 7, Section 7.4.

Implementations

impl UChart

pub fn new() -> Self

Create a new U chart.

pub fn add_sample(&mut self, defects: u64, units_inspected: f64)

Add a sample with the number of defects and the number of units inspected.

The units_inspected can be fractional (e.g., area or length). Ignores samples where units_inspected <= 0 or is not finite.

pub fn u_bar(&self) -> Option<f64>

Get the overall defect rate (u-bar), or None if no data.

pub fn points(&self) -> &[AttributeChartPoint]

Get all chart points.

pub fn is_in_control(&self) -> bool

Check if the process is in statistical control.

Trait Implementations

impl Default for UChart

fn default() -> Self

Returns the “default value” for a type.