Environmental Test Chambers & Reliability Labs worked example

Sample Size Planning with qualification lots or builds of 7.5 lots: a worked example

Push qualification lots or builds up to 7.5 lots and the picture changes. This example computes every intermediate figure at that operating point. a validation engineer needs the total samples required by a qualification matrix

The inputs for this scenario

  • Qualification lots or builds: 7.5 lots (raised for this scenario; the documented default is 3)
  • Stress cells per lot: 6 cells / lot (unchanged)
  • Samples per stress cell: 12 samples (unchanged)

Working through the calculation

  • Applying the documented formula (Total planned samples = qualification lots × stress cells per lot × samples per stress cell) to the inputs above produces each figure below.
  • At this operating point the engine returns 540 samples for total reliability test samples, the number this scenario is built around.
  • At this operating point the engine returns 27 hr for estimated sample handling hours.
  • At this operating point the engine returns 6 lots for qualification lots or builds.
  • At this operating point the engine returns 12 samples for samples per stress cell.

How this compares with the baseline

  • Against the tool's baseline example, where qualification lots or builds sits at 3 lots and the headline result is 216 samples, this scenario comes in 150% above the baseline at 540 samples.
  • It computes the total number of test samples a qualification consumes by multiplying lots, stress cells per lot, and samples per cell, and estimates the associated handling hours. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Total reliability test samples: 540 samples (headline result)
  • Estimated sample handling hours: 27 hr
  • Qualification lots or builds: 6 lots
  • Samples per stress cell: 12 samples

Run it with your numbers

  • Every input above is editable in the live Sample Size Planning calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.