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SPC software · Mac & Windows

SPC software for control charting and process capability.

Know whether the process is in control and capable — and be able to show how certain that is. Nine control charts with all eight Nelson rules, Phase I/II staging, and capability reported with confidence intervals rather than a bare point estimate. Native on Mac and Windows, bought once. Free to try on your own data before you decide.

9
Control-chart types
~5M
Rows, smoothly
Once
One payment, not annual
2
Platforms, equally native
An EWMA control chart of conductivity with control limits and out-of-control points flagged
Drift, caught early. An EWMA chart of conductivity with its control limits and every out-of-control point flagged — the small sustained shifts a Shewhart chart is slow to see.
A process capability report in Stratum showing Cp, Cpk, Cpm, Pp and Ppk with 95% confidence intervals beside a capability histogram with specification limits
Capability, with the interval. Every index reported with a confidence interval — from the exact noncentral t, not a normal approximation — and a normality check that says so when the model does not fit.
An X-bar and R chart in Stratum split into a Phase I baseline and a Phase II monitoring stage: the baseline limits run flat across the divider and catch a drift at subgroups 37 to 39
Baseline, then monitoring. Limits estimated from the Phase I period and carried flat across everything after it — which is exactly what catches the drift at subgroups 37 to 39. Or re-estimate them per stage, your choice.
A p-chart in Stratum whose control limits step with each lot's inspected quantity, with one point flagged above the limit
Variable-width limits. Limits that step with each subgroup’s size — p, np, c and u, not just p and c — so a smaller subgroup is judged against its own, wider, limit.
X-bar and R chart of 25 baseline batches, all in control
X̄ and R, in control. Baseline batches with computed limits — establish the process before you judge it.

SPC in Stratum

A subscription doesn't end. A one-time purchase does.

Subscription SPC tools

Most SPC and quality suites are sold as an annual subscription — often quoted only after a sales call. Whatever the number turns out to be, it returns every year, and access stops when you stop paying.

Yr 1Pay Yr 2Pay Yr 3Pay Yr 4Pay Yr 5Pay

Five years, five bills — and no software left if you stop.

Stratum

Bought once. The version you buy keeps working forever, online or off, on Mac and Windows alike.

Yr 2— Yr 3— Yr 4— Yr 5—

$249 for Professional — once, and it's yours.

CapabilityIn Stratum
Variables control chartsI-MR (individuals & moving range), X̄-R and X̄-S for subgrouped data
Attributes control chartsp, np, c and u charts, with variable-width limits for unequal subgroup sizes
Time-weighted chartsTabular CUSUM with FIR head start; EWMA with time-varying limits
Out-of-control rulesAll eight Nelson rules, toggled per chart, with a Western Electric preset
Phases & stagesEstimate from a Phase I baseline and carry the limits forward, or re-estimate per stage
Control limitsEstimated from your data, or given from historical and standard values
Within-sigma estimatorsPooled SD, S̄, R̄ or average moving range — with unbiasing constants
Process capabilityCp, Cpk, CPL, CPU, Cpm, Pp, Ppk, PPL, PPU, observed and expected PPM, Z-bench within and overall, capability histogram
Capability intervalsConfidence intervals on every index, from the exact noncentral t rather than a normal approximation
Non-normal capabilityLognormal, Weibull and exponential fits with percentile indices to ISO 22514-2, and a fit test behind the choice
Linked selectionSelect points on a control chart and the same rows highlight in the datasheet and every other chart
Everyday stats & charts30+ charts, ANOVA, regression, contingency
Data inCSV, Excel, fixed-width ASCII, SPSS .sav and Stata .dta — to ~5 million rows
Numerical validationPublished validation record — the outside tool named for every statistic, including the gaps
PricingOne-time (Professional $249) — no subscription
Where your SPC analyses live in Stratum — menu path by menu path
Individuals & moving-range chart (I-MR)

Control Charts — I-MR for individual measurements, with control limits and all eight Nelson rules.

Subgrouped variables chart (X̄)

Control Charts — X̄-R and X̄-S, plotting subgroup means against limits from the range or the standard deviation, your choice.

Attributes charts for defectives / defects

Attribute Charts — p and np for defectives, c and u for defects, with variable-width limits for unequal subgroup sizes.

Which parts were those, exactly

Linked Selection — drag a rectangle around the out-of-control points and the same rows light up in the datasheet and in every other chart, so a violation leads straight back to the units behind it.

Baseline period, then ongoing monitoring

Phases & Stages — estimate limits from a Phase I baseline and extend them across everything after it, or re-estimate inside each stage when the process is meant to have changed.

Capability on data that is not normal

Distribution Fit — fit a lognormal, Weibull or exponential, then compute the indices from the fitted percentiles the ISO 22514-2 way, with the goodness-of-fit test alongside.

Small-shift detection

CUSUM & EWMA — tabular CUSUM with FIR head start, and EWMA with time-varying limit widths.

Process capability study

Process Capability — Cp, Cpk, Cpm, Pp, Ppk, PPM and Z-bench, with within and overall sigma side by side, confidence intervals on every index, and a capability histogram.

Descriptive statistics & hypothesis tests

Summary, ANOVA, t-tests — means, SD, quartiles; one-way ANOVA with Tukey HSD; two-sample and paired t, with non-parametric equivalents.

Regression & relationships

Linear Regression — coefficients with CIs, VIF, leverage, Cook's D, R², AIC and BIC.

Everyday charts

30+ chart types — histogram, box, violin, density, Pareto, scatter with OLS/LOESS, treemap, mosaic and more.

Point-and-click throughout — and equally native on a Mac, where most SPC suites are Windows-first.

What you get for quality work

Stratum's Professional edition includes SPC control charts and full process-capability analysis (Cp, Cpk, Pp, Ppk, and PPM) alongside the everyday toolkit — descriptive statistics, ANOVA, correlation, contingency tests, and regression with diagnostics — plus data mining (decision trees, random forests, boosted trees, clustering) and multivariate methods (PCA, correspondence analysis, MANOVA). Import your .csv, .xlsx, fixed-width ASCII, SPSS .sav or Stata .dta and try it on your own process data first.

Frequently asked questions

Which control charts does Stratum support?

Nine: I-MR (individuals and moving range), X̄-R and X̄-S for subgrouped data, p and np for defectives, c and u for defects, and CUSUM and EWMA for time-weighted monitoring — with all eight Nelson rules, toggled per chart.

Does it calculate Cp and Cpk?

Yes — Cp, Cpk, CPL, CPU and Cpm against your specification limits, with Pp, Ppk, PPL and PPU on the overall sigma, observed and expected PPM, Z-bench within and overall, and a capability histogram. Each index is reported with a confidence interval, computed from the exact noncentral t.

Can it handle a baseline period and later stages?

Yes. Point a phase column at the run and Stratum will either estimate the limits from the Phase I baseline and carry them forward, or re-estimate the center and limits inside each stage. You can also supply limits directly from historical or standard values instead of estimating them.

What if my data is not normal?

Fit a lognormal, Weibull or exponential distribution and Stratum computes the capability indices from the fitted percentiles, following ISO 22514-2, with the goodness-of-fit test shown next to the choice.

Does Stratum run on Mac?

Yes — Stratum is a native app for both macOS 14+ and Windows 10/11, so SPC works the same on either.

Is it a subscription?

No — Stratum is a one-time purchase. You can upgrade from Standard to Professional later.