Is a 1.5-sigma shift assumed?

No. The shift comes directly from the two entered means and reference SD. A fixed reporting convention is not a measured process change.

Why can the shift be negative?

The current mean is below the reference mean. Its signed change moves away from the upper specification limit shown here.

Does this prove a significant mean change?

No. A significance test needs sample sizes, variability estimates and an appropriate study design. This calculator reports the measured standardized difference.

Can current process variation change?

Yes. This comparison deliberately holds the reference SD fixed. Analyze current variability separately before drawing a capability conclusion.

Quality & Metrology calculator

Measured Sigma Shift Calculator

Express a measured change in process mean in reference standard deviations and show its effect on upper-limit clearance.

What this calculator does

Express a measured change in process mean in reference standard deviations and show its effect on upper-limit clearance.

Formula used

Signed sigma shift = (current mean − reference mean) ÷ reference SD
Mean change = current mean − reference mean
Reference upper-limit Z = (upper limit − reference mean) ÷ reference SD
Current upper-limit Z = (upper limit − current mean) ÷ reference SD

Inputs explained

Reference Process Mean: Mean from the stable reference study.
Current Process Mean: Mean from the comparison study using the same characteristic.
Reference Within Standard Deviation: Within-process SD from the reference study.
Upper Specification Limit: Upper specification for the characteristic being compared.

How to use the result

Best suited to lower reference Upper-Limit Z, higher reference Upper-Limit z.
This descriptive mean change is not a significance test or long-term capability prediction. Upper-limit clearance does not evaluate a lower specification limit.

Current U.S. benchmarks

U.S. manufacturing runs at 75.7% of capacity (Federal Reserve, Aug 2026). New factory orders are up 8.5% year over year (Census).

Common questions

Is a 1.5-sigma shift assumed? No. The shift comes directly from the two entered means and reference SD. A fixed reporting convention is not a measured process change.
Why can the shift be negative? The current mean is below the reference mean. Its signed change moves away from the upper specification limit shown here.
Does this prove a significant mean change? No. A significance test needs sample sizes, variability estimates and an appropriate study design. This calculator reports the measured standardized difference.
Can current process variation change? Yes. This comparison deliberately holds the reference SD fixed. Analyze current variability separately before drawing a capability conclusion.

Last reviewed 2026-10-06.