SPC Study | QualityFirst

Build a one-time Phase I control-chart study for individual observations or rational subgroups. Select the baseline, choose the rules to evaluate and review every detected signal before interpreting process stability.

Phase I analytical study This tool analyses an uploaded data snapshot. It does not continuously monitor a production database or store an approved Phase II baseline.

1. Data

Measurement data

CSV / XLSX file:

Upload a CSV or XLSX file. QualityFirst identifies workbook sheets, probable table headers and available columns before study configuration is required.

2. Study setup

Column mapping

Measurement column:

Subgroup column:

Timestamp column:

Baseline / phase column:

Timestamp is optional. When supplied, observations are sorted chronologically before calculation.

Chart and subgroup structure

Chart type:

Subgroup mode:

Sequential subgroup size:

Automatic selection uses I-MR for individual values, Xbar-R for subgroup sizes 2-10 and Xbar-S for sizes 11-25. Unequal subgroup sizes are rejected transparently.

Control-limit basis

Limit mode:

Baseline method:

Baseline count:

Baseline column value:

Estimate limits from a defined Phase I baseline and apply the frozen limits to all displayed observations.

Known control limits

Primary chart

Primary LCL:

Primary CL:

Primary UCL:

Secondary chart

Secondary LCL:

Secondary CL:

Secondary UCL:

SPC rule evaluation

Rule 1 – one point beyond 3 sigma

Rule 2 – nine points on one side of CL

Rule 3 – six points increasing or decreasing

Rule 4 – fourteen points alternating

Rules 2-4 are evaluated on the Individuals or Xbar chart. The MR, R and S chart uses Rule 1 only.

Documented baseline exclusions

Exclude from baseline:

Comma-separated observation numbers (I-MR) or subgroup labels.

Documented special-cause reason:

Use only for a confirmed special cause. Excluded points remain visible in the chart and report.

Study identification

Study name:

Unit:

Optional information used to identify the study and label measurement values in the report.