QM Bench

About QM Bench

QM Bench is a set of free tools for quality and manufacturing engineers. It is built for the everyday questions: is the process capable, is it stable, can the gauge be trusted, what should be fixed first.

Calculation methods

  • Capability: within sigma from R̄/d₂, S̄/c₄ or MR̄/1.128 (pooled over subgroups when sizes differ), overall sigma from the sample standard deviation. Cpk confidence interval by the Bissell approximation. Cm and Cmk with 8 and 4 sigma as in VDA volume 4.
  • Non-normal capability: maximum likelihood fits of lognormal, Weibull, gamma and exponential distributions, ranked by Anderson-Darling A², and the ISO 22514-2 percentile method (0.135 %, 50 %, 99.865 % quantiles). Box-Cox with maximum likelihood lambda.
  • Control charts: X-bar/R, X-bar/S and I-MR with standard constants, Nelson rules 1 to 8, limits from all data, from the first subgroups or fixed; EWMA (Montgomery, exact time-varying limits) and tabular CUSUM; p, np, c and u charts with per-sample limits.
  • Normality: Anderson-Darling with the Stephens small-sample correction; probability plots with Benard median ranks.
  • Gage R&R: crossed two-way ANOVA, interaction pooled when p ≥ 0.25, and the AIAG average and range method (K1, K2, K3). Verdict per AIAG MSA 4th edition.
  • Type 1 study: Cg = (K·T)/(6s), Cgk = (K·T/2 − |bias|)/(3s), one-sample t-test for the bias.
  • Linearity and bias: least-squares regression of bias on reference value with t-tests and a 95 % confidence band (AIAG MSA).
  • Attribute agreement: within, between and versus standard agreement with Clopper-Pearson intervals, Fleiss' and Cohen's kappa.
  • FMEA: RPN with configurable thresholds or the AIAG-VDA (2019) action priority table.
  • Sampling: ISO 2859-1 single sampling, normal inspection; OC curves from the binomial distribution; sample size formulas for means, proportions, zero-failure tests and Cpk confidence.

Validation

An automated test compares every engine with independent NumPy and SciPy calculations and with published reference values (AIAG MSA example, ISO 2859-1 tables, control chart constants). The current results are in the validation report.

Privacy

All calculations run in your browser. See the privacy page.