Struct PChart 

pub struct PChart { /* private fields */ }

Proportion nonconforming (P) chart.

Monitors the fraction of defective items in samples that may have different sizes. Control limits vary per subgroup when sample sizes differ.

Formulas

• CL = p-bar = total_defectives / total_inspected
• UCL_i = p-bar + 3 * sqrt(p-bar * (1 - p-bar) / n_i)
• LCL_i = max(0, p-bar - 3 * sqrt(p-bar * (1 - p-bar) / n_i))

Examples

use u_analytics::spc::PChart;

let mut chart = PChart::new();
chart.add_sample(3, 100);  // 3 defectives out of 100
chart.add_sample(5, 100);
chart.add_sample(2, 100);
chart.add_sample(4, 100);

let p_bar = chart.p_bar().expect("should have p_bar after adding samples");
assert!(p_bar > 0.0);

Reference

Montgomery, D.C. (2019). Introduction to Statistical Quality Control, 8th ed., Chapter 7, Section 7.3.

Implementations

impl PChart

pub fn new() -> Self

Create a new P chart.

pub fn add_sample(&mut self, defectives: u64, sample_size: u64)

Add a sample with the number of defective items and the total sample size.

Ignores samples where defectives > sample_size or sample_size == 0.

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

Get the overall proportion defective (p-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 PChart

fn default() -> Self

Returns the “default value” for a type.