{"id":"wpc-tech100-article-088-en","slug":"comparing-wpc-means-ranges-and-lower-bound-values","locale":"en","url":"https://woodplasticcomposite.net/guides/comparing-wpc-means-ranges-and-lower-bound-values/","title":"Comparing WPC means, ranges and lower-bound values","answer":"An average test result and a design value are not interchangeable. Technical comparisons should identify whether a number is a mean, a minimum observation or a statistically derived value.","author":"NFC & WPC Knowledge Reference","faqIds":["wpc-tech100-faq-088-en"],"tagIds":[],"noindex":false,"related":["wpc-tech100-article-089-en"],"version":1,"modified":"2026-10-15","reviewer":"","sections":[{"id":"technical-context","text":"The sample size and variability affect interpretation. The lowest result in a small series is not automatically a reliable lower bound for future production. Likewise, a high average can conceal a wide spread.","heading":"Technical context","references":[],"url":"https://woodplasticcomposite.net/guides/comparing-wpc-means-ranges-and-lower-bound-values/#technical-context"},{"id":"verification-plan","text":"Request individual results or a suitable summary, the number of specimens and the derivation of any declared value. Check the applicable assessment method with the responsible engineer. Do not invent a universal reduction factor from a generic article.","heading":"What to measure and document","references":[],"url":"https://woodplasticcomposite.net/guides/comparing-wpc-means-ranges-and-lower-bound-values/#verification-plan"},{"id":"practical-decision","text":"Use like-for-like quantities when comparing products. A supplier reporting a conservative declared value may appear weaker than one advertising an average, even when that conclusion is unwarranted. Clear definitions are more useful than a simple strength ranking.","heading":"Implications for development and specification","references":[],"url":"https://woodplasticcomposite.net/guides/comparing-wpc-means-ranges-and-lower-bound-values/#practical-decision"},{"id":"reading-scope","text":"General engineering-statistics guidance; not a WPC product standard. Use the linked work as related reading. The practical checks above are editorial recommendations, not reported test results or a substitute for product qualification.","heading":"Related reading and evidence limits","references":[1],"url":"https://woodplasticcomposite.net/guides/comparing-wpc-means-ranges-and-lower-bound-values/#reading-scope"}],"seoTitle":"Comparing WPC means, ranges and lower-bound values | WPC Reference","topicIds":[],"published":"2026-10-15","tableText":"Review step | Evidence to retain\nMaterial and geometry | Exact specimen or product identity\nVerification | Method, conditions and individual observations\nDecision | Approved scope and documented limitations","takeaways":"The sample size and variability affect interpretation.\nRequest individual results or a suitable summary, the number of specimens and the derivation of any declared value.\nUse like-for-like quantities when comparing products.","aiAssisted":true,"categoryId":"wpc-tech100-category-4","reviewedAt":"","change_note":"New focused technical draft; not a product certification or production recipe.","description":"An average test result and a design value are not interchangeable.","heroImageId":"","referenceIds":["wpc-tech100-ref-statistics"],"review_status":"AI-assisted English editorial draft. Human technical review has not been recorded.","table_caption":"Evidence checklist for comparing wpc means, ranges and lower-bound values","seoDescription":"An average test result and a design value are not interchangeable.","translationGroup":"wpc-tech100-088-2026","references":[{"url":"https://www.itl.nist.gov/div898/handbook/","type":"web","title":"NIST engineering statistics handbook","noindex":false,"accessed":"2026-10-14","seoTitle":"NIST engineering statistics handbook","publisher":"NIST","description":"Related reading; scope and limitations are identified in each article.","seoDescription":"Related reading; scope and limitations are identified in each article."}],"faqs":[{"question":"What evidence is needed for comparing WPC means, ranges and lower-bound values?","answer":"Request individual results or a suitable summary, the number of specimens and the derivation of any declared value. Check the applicable assessment method with the responsible engineer. Do not invent a universal reduction factor from a generic article."}]}