Did the new shift improve finishing quality?
Study design
Match line-weeks on fabric family, order size and operator experience. Alternate shift patterns where staffing permits.
Instrument and data fields
Record line, week, shift pattern, fabric, inspected batches and batches requiring rework.
Simulated evidence
Matched cotton lots: 12 of 120 reworked under staggered shifts, 17 of 120 under current shifts. Synthetic lots: 14 of 100 versus 13 of 100.
Check before drawing a conclusion
Write down the comparison you would make and the unit each row represents. Identify one explanation the study design cannot rule out, then describe how it would affect the decision.
Reveal the worked analysis
Cotton rework falls by about 4.2 points, while synthetic rework rises by 1 point. Run another rotation and monitor handoff defects by material.
Matched weeks control measured differences only. Unrecorded machine condition or order complexity can still bias the comparison.