About QualityNest

QualityNest is a lightweight, browser-based quality engineering toolkit. The initial version provides process capability and Individuals–Moving Range analysis.

Calculation methods

Overall standard deviation: sample standard deviation, denominator n−1. Within estimate for individuals: average moving range of consecutive observations divided by d2 = 1.128. Within estimate for rational subgroups: average subgroup sample standard deviation divided by c4 for subgroup size n.

Cp = (USL−LSL)/(6σwithin); Cpk = min((USL−mean)/(3σwithin),(mean−LSL)/(3σwithin)); Pp/Ppk use overall sample standard deviation instead.

I-MR limits: Individuals center = mean, limits = mean ± 3(MR-bar/1.128). Moving range center = MR-bar, UCL = 3.267×MR-bar, LCL = 0.

Important limitations

Measurements must be collected in meaningful time order. The application does not establish normality, rational subgrouping, measurement-system adequacy, independence, or process stability. Control limits are not specification limits. Zero variation results in unavailable indices. PDF summaries do not embed charts in v1.

Before production or customer reporting, verify calculations and assumptions against independently validated software and your organization's procedures.