An estimate is 19.7 N with expanded uncertainty ±0.5 N. A minimum of 20.0 N is required, and acceptance requires the full interval above the minimum. What decision follows?
A Acceptance cannot be shown
B It is certainly below
C Acceptance is guaranteed
D It is certainly above
Answer: A. Acceptance cannot be shown. The interval from 19.2 N to 20.2 N crosses the limit, so it does not meet the stated acceptance rule.
Two textiles match under daylight but diverge under incandescent light, despite being measured at the same geometry. Which effect fits this observation?
A Progressive colour bleeding
B Elastic hysteresis
C Illuminant metamerism
D Progressive abrasion loss
Answer: C. Illuminant metamerism. Different spectral reflectances can give the same perceived colour under one illuminant and different colours under another.
During tensile testing, crosshead travel is 30 mm and independently measured elastic machine compliance accounts for 4 mm. For an initial gauge length of 125 mm, find corrected strain.
A 13.3%
B 27.2%
C 24.0%
D 20.8%
Answer: D. 20.8%. Corrected specimen extension is 30 − 4 = 26 mm. Divide by 125 mm and multiply by 100.
Under a stepped abrasion inspection, an intact specimen is seen at 12,000 cycles and first seen damaged at 16,000 cycles. What is the finest interval supported by these observations?
A 12,000 < cycles ≤ 16,000
B Cycles > 16,000
C Exactly 16,000 cycles
D Exactly 12,000 cycles
Answer: A. 12,000 < cycles ≤ 16,000. The endpoint occurred after the last intact inspection and no later than the first damaged inspection.
Five replicates have mean strength 48 N and sample standard deviation 2.4 N. Find the coefficient of variation.
A 2.4%
B 5.0%
C 50.0%
D 20.0%
Answer: B. 5.0%. Divide standard deviation by the mean and multiply by 100: 2.4/48 × 100%.
Draped projection including the support disc is 180 cm². Flat area is 300 cm² and disc area is 60 cm². Using areas outside the disc, find the drape coefficient.
A 40%
B 60%
C 50%
D 75%
Answer: C. 50%. Subtract the support area from both quantities: (180 − 60)/(300 − 60) = 120/240.
At the same pressure difference, the exposed test area doubles. If local permeability is uniform, what happens to the total steady air flow?
A It doubles
B It remains constant
C It falls to half
D It rises fourfold
Answer: A. It doubles. At the same pressure difference and uniform local behaviour, total flow is proportional to exposed area.
Fastness grade is 4 under one method and 2 under a more severe exposure. Which report supports correct interpretation?
A Report only the higher grade
B Give conditions with results
C Convert grades to percentages
D Average both grades blindly
Answer: B. Give conditions with results. Ratings are linked to the specific procedure and exposure. Conditions must accompany each result for it to be interpretable.
Sampling finds two failed specimens out of ten from the edge and one failed specimen out of thirty from the centre. What is the observed edge failure rate relative to the centre?
A Three times as high
B Two times as high
C One sixth as high
D Six times as high
Answer: D. Six times as high. The respective rates are 2/10 and 1/30. Their ratio is 6.
Crosshead speed is 20 mm/min over a 100 mm initial gauge. If crosshead displacement equals specimen extension, what is nominal strain rate?
A 20% per minute
B 0.2% per minute
C 2% per minute
D 200% per minute
Answer: A. 20% per minute. Divide the extension rate by gauge length: 20/100 = 0.20 per minute.
A fabric reports 28, 30 and 32 N in warp tests and 40, 42 and 44 N in weft tests. What is the weft-to-warp mean ratio?
A 0.71
B 1.60
C 1.27
D 1.40
Answer: D. 1.40. The warp mean is 30 N and the weft mean is 42 N, so the ratio is 42/30.
Two CIELAB readings have equal L*. From specimen one to specimen two, a* falls from +4 to +1 and b* rises from −1 to +3. In which directions did the chromatic coordinates move?
A Greener and yellower
B Redder and bluer
C Redder and yellower
D Greener and bluer
Answer: A. Greener and yellower. A lower a* is a movement toward green. A higher b* is a movement toward yellow.
Control checking finds instrument repeatability standard deviation of 0.6 N and independent specimen variability of 0.8 N. What total standard deviation follows from variance addition?
A 1.4 N
B 0.7 N
C 1.0 N
D 0.2 N
Answer: C. 1.0 N. Independent variances add. The total standard deviation is the square root of 0.6² + 0.8².
After 20,000 cycles, tested fabric mass drops from 2.50 g to 2.35 g. What is the average loss per 1,000 cycles?
A 75 mg
B 0.75 mg
C 7.5 mg
D 15 mg
Answer: C. 7.5 mg. Total loss is 0.15 g or 150 mg. Over twenty blocks of 1,000 cycles the average is 7.5 mg per block.
Machine travel increases from 0 to 5 mm while force rises linearly from 0 to 20 N. Estimate the work input for that segment.
A 0.100 J
B 0.010 J
C 50 J
D 0.050 J
Answer: D. 0.050 J. The area under the force–displacement line is a triangle: one half × 20 N × 0.005 m.
One reflectance test includes specular glare while another excludes it. What change allows a direct colour comparison?
A Average different geometries
B Use identical optical geometry
C Change the fibre blend
D Compare only larger values
Answer: B. Use identical optical geometry. Including or excluding specular reflection changes the measurement. Comparative readings should use the same geometry.
Assume linear force calibration gives 103 N for a true 100 N and zero error at zero force. What corrected load corresponds to an indicated 51.5 N?
A 50 N
B 51.5 N
C 53.0 N
D 48.5 N
Answer: A. 50 N. In this calibration the indicated value is 1.03 times true load. Divide 51.5 N by 1.03.
In a vertical wicking comparison, rise follows h² proportional to time. At 1 min the rise is 12 mm, so what rise is predicted after 4 min?
A 48 mm
B 24 mm
C 6 mm
D 36 mm
Answer: B. 24 mm. With that model height scales with the square root of time. Quadrupling elapsed time doubles height.
For results 28, 30, 32 and 34 N, what is sample standard deviation to two decimal places?
A 2.00 N
B 2.58 N
C 3.33 N
D 2.24 N
Answer: B. 2.58 N. The mean is 31 N and the sum of squared deviations is 20 N². The sample variance is 20/3 N². Take its square root.
Recorded garment length is 3% below its original value but width is 2% above its original value. Find area change for a rectangular piece.
A 1.00% increase
B 5.06% decrease
C 1.06% decrease
D 5.00% decrease
Answer: C. 1.06% decrease. The area ratio is 0.97 × 1.02 = 0.9894, a decrease of 1.06%.
A grey calibration tile has a certified reflectance but the instrument records a lower reading on repeated trials. Which effect does that demonstrate?
A Higher fabric fastness
B Greater fabric abrasion
C Only random sampling noise
D Systematic measurement bias
Answer: D. Systematic measurement bias. Repeated readings on the same reference that consistently deviate in one direction indicate a measurement offset.
Loading work is 0.40 J. Unloading returns 0.28 J. Find the hysteresis energy loss.
A 0.68 J
B 0.12 J
C 0.28 J
D 0.40 J
Answer: B. 0.12 J. Energy loss equals loading work less returned energy, or 0.40 − 0.28 J.
Humidity trials use different tensile instruments for the same lot. Which change better isolates humidity as the cause of any difference?
A Increase yarn count
B Switch both specimen lots
C Use the same instrument
D Pool force results immediately
Answer: C. Use the same instrument. Conditioning atmosphere should be the main changed factor. Holding the instrument constant reduces confounding.
Load at rupture is 72 N for a test strip 30 mm wide. Express the force per unit width in N/cm.
A 36 N/cm
B 216 N/cm
C 24 N/cm
D 2.4 N/cm
Answer: C. 24 N/cm. Thirty millimetres is 3 cm. Divide 72 N by 3 cm.
Increasing independent replicates from four to sixteen leaves sample variance unchanged. How does the estimated standard error of the mean change?
A It stays unchanged
B It quadruples
C It doubles
D It halves
Answer: D. It halves. Standard error scales as one over the square root of the number of replicates, with standard deviation held fixed.