Calculate Polyester Reinforcement Basis-Weight Variation from a Sample Set
A nominal 180 g/m² label does not describe variation across every sample. Keep the mean, individual results and variation calculation separate when agreeing how to evaluate a polyester reinforcement grade.
Separate the quantities
Basis weight is mass divided by area. A sample’s g/m² result, the average of several samples and their variation describe different things. Record the sampled area and measured mass with the calculation.
For example, a 0.1 m² specimen weighing 18 g corresponds to 180 g/m². That single result does not establish the variation of the roll or lot.
Agree the calculation convention
A coefficient of variation is the standard deviation divided by the mean, multiplied by 100%. Agree the sampling plan and whether the calculation uses sample or population standard deviation.
Consider the illustrative results 170, 180 and 190 g/m². Their mean is 180. Using sample standard deviation gives 10 g/m² and a coefficient of variation of approximately 5.56%. These illustrative values explain the calculation; they are not batch test results.
Illustrative calculation, not batch data
On a phone, swipe the table sideways to see every column.
| Item | Value / meaning |
|---|---|
| Example results | 170, 180, 190 g/m² |
| Mean | 180 g/m² |
| Sample standard deviation | 10 g/m² |
| Coefficient of variation | 10 ÷ 180 × 100 = 5.56% |
| Individual tolerance | Requires a separate agreed definition |
Read the grade table correctly
The published continuous-filament polyester table gives 10% for mass coefficient of variation in its listed columns. Keep that requirement attached to the applicable grade and agreed evaluation basis.
Do not interpret the row as an automatic ±10% tolerance for every individual sample. A coefficient of variation and an individual acceptance band need different definitions.
Make the RFQ testable
Provide the nominal grade, required acceptance criteria, sampling locations and calculation convention. If your plant uses a specific method, identify it for confirmation rather than assuming a catalogue row defines every detail.
Send the requirement with the selected width and roll format. This lets the purchasing comparison distinguish nominal supply size from the statistical property your quality team needs.
Questions for This Purchase
Is coefficient of variation the same as ± tolerance?
No. They express different acceptance concepts.
Does one sample establish roll uniformity?
It establishes only that sample’s result; agree a suitable sampling plan.
Are the example values a Merily inspection report?
No. They demonstrate the calculation only.
Send your specification.
Get a clear material quote.
Tell us what you produce, the material you need and your required roll format. Include the quantity and destination port so we can prepare the product and packing details together.
Useful details: thickness or basis weight, width, roll length or weight, core, quantity and application. For release film, add coated side and release requirements.
Standard production: approximately 10 days for one 40-ft container order. Customized specifications: approximately 10–15 days. Confirm the schedule with the final order.