Acceptable Quality Level (AQL) Sample Size Calculator
ANA›Life Services Authority›National Calculator Authority›Acceptable Quality Level (AQL) Sample Size Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
Acceptable Quality Level (AQL) Sample Size Calculator
Determine the required sample size and acceptance/rejection numbers for lot inspection using the ANSI/ASQ Z1.4 standard (attribute sampling).
Lot Size (N)
AQL Level (%)
0.065 0.10 0.15 0.25 0.40 0.65 1.0 1.5 2.5 4.0 6.5 10.0
Inspection Level
Level I (Reduced) Level II (Normal) Level III (Tightened)
Inspection Type
Normal Tightened Reduced
Calculate ...
function accCalc() { const lotSize = parseFloat(document.getElementById('acc-lot-size').value); const aql = parseFloat(document.getElementById('acc-aql').value); const inspLevel = document.getElementById('acc-inspection-level').value; const inspType = document.getElementById('acc-inspection-type').value;
if (isNaN(lotSize) || lotSize Please enter a valid positive integer for Lot Size.'; return; }
// ANSI/ASQ Z1.4 Table I: Lot size ranges -> Sample Size Code Letter // [minLotSize, maxLotSize, levelI_code, levelII_code, levelIII_code] const lotSizeTable = [ [2, 8, 'A', 'A', 'B'], [9, 15, 'A', 'B', 'C'], [16, 25, 'B', 'C', 'D'], [26, 50, 'C', 'D', 'E'], [51, 90, 'C', 'E', 'F'], [91, 150, 'D', 'F', 'G'], [151, 280, 'E', 'G', 'H'], [281, 500, 'F', 'H', 'J'], [501, 1200, 'G', 'J', 'K'], [1201, 3200, 'H', 'K', 'L'], [3201, 10000, 'J', 'L', 'M'], [10001, 35000, 'K', 'M', 'N'], [35001, 150000, 'L', 'N', 'P'], [150001, 500000, 'M', 'P', 'Q'], [500001, Infinity,'N', 'Q', 'R'], ];
// Sample size per code letter const sampleSizeMap = { 'A': 2, 'B': 3, 'C': 5, 'D': 8, 'E': 13, 'F': 20, 'G': 32, 'H': 50, 'J': 80, 'K': 125, 'L': 200,'M': 315,'N': 500,'P': 800,'Q': 1250,'R': 2000 };
// ANSI/ASQ Z1.4 Table II-A (Normal), II-B (Tightened), II-C (Reduced) // Structure: codeLetter -> { aqlValue: [Ac, Re] } // Ac = Acceptance Number, Re = Rejection Number // Arrow up (↑) means use first sampling plan above; arrow down (↓) means use first below. // We encode arrows as special strings and resolve them.
const normalTable = { // code: { aql: [Ac, Re] } null means use arrow 'A': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null,'0.65':null, '1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[0,1],'6.5':[0,1],'10.0':[0,1] }, 'B': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null,'0.65':null, '1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[0,1],'6.5':[0,1],'10.0':[1,2] }, 'C': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null, '0.65':[0,1],'1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[1,2],'6.5':[1,2],'10.0':[2,3] }, 'D': { '0.065':null,'0.10':null,'0.15':null,'0.25':null, '0.40':[0,1],'0.65':[0,1],'1.0':[0,1],'1.5':[1,2],'2.5':[1,2],'4.0':[2,3],'6.5':[3,4],'10.0':[3,4] }, 'E': { '0.065':null,'0.10':null,'0.15':null, '0.25':[0,1],'0.40':[0,1],'0.65':[0,1],'1.0':[1,2],'1.5':[1,2],'2.5':[2,3],'4.0':[3,4],'6.5':[5,6],'10.0':[7,8] }, 'F': { '0.065':null,'0.10':null, '0.15':[0,1],'0.25':[0,1],'0.40':[0,1],'0.65':[1,2],'1.0':[1,2],'1.5':[2,3],'2.5':[3,4],'4.0':[5,6],'6.5':[7,8],'10.0':[10,11] }, 'G': { '0.065':null, '0.10':[0,1],'0.15':[0,1],'0.25':[0,1],'0.40':[1,2],'0.65':[1,2],'1.0':[2,3],'1.5':[3,4],'2.5':[5,6],'4.0':[7,8],'6.5':[10,11],'10.0':[14,15] }, 'H': { '0.065':[0,1],'0.10':[0,1],'0.15':[0,1],'0.25':[1,2],'0.40':[1,2],'0.65':[2,3],'1.0':[3,4],'1.5':[5,6],'2.5':[7,8],'4.0':[10,11],'6.5':[14,15],'10.0':[21,22] }, 'J': { '0.065':[0,1],'0.10':[0,1],'0.15':[1,2],'0.25':[1,2],'0.40':[2,3],'0.65':[3,4],'1.0':[5,6],'1.5':[7,8],'2.5':[10,11],'4.0':[14,15],'6.5':[21,22],'10.0':[21,22] }, 'K': { '0.065':[0,1],'0.10':[1,2],'0.15':[1,2],'0.25':[2,3],'0.40':[3,4],'0.65':[5,6],'1.0':[7,8],'1.5':[10,11],'2.5':[14,15],'4.0':[21,22],'6.5':[21,22],'10.0':[21,22] }, 'L': { '0.065':[1,2],'0.10':[1,2],'0.15':[2,3],'0.25':[3,4],'0.40':[5,6],'0.65':[7,8],'1.0':[10,11],'1.5':[14,15],'2.5':[21,22],'4.0':[21,22],'6.5':[21,22],'10.0':[21,22] }, 'M': { '0.065':[1,2],'0.10':[2,3],'0.15':[3,4],'0.25':[5,6],'0.40':[7,8],'0.65':[10,11],'1.0':[14,15],'1.5':[21,22],'2.5':[21,22],'4.0':[21,22],'6.5':[21,22],'10.0':[21,22] }, 'N': { '0.065':[2,3],'0.10':[3,4],'0.15':[5,6],'0.25':[7,8],'0.40':[10,11],'0.65':[14,15],'1.0':[21,22],'1.5':[21,22],'2.5':[21,22],'4.0':[21,22],'6.5':[21,22],'10.0':[21,22] }, 'P': { '0.065':[3,4],'0.10':[5,6],'0.15':[7,8],'0.25':[10,11],'0.40':[14,15],'0.65':[21,22],'1.0':[21,22],'1.5':[21,22],'2.5':[21,22],'4.0':[21,22],'6.5':[21,22],'10.0':[21,22] }, 'Q': { '0.065':[5,6],'0.10':[7,8],'0.15':[10,11],'0.25':[14,15],'0.40':[21,22],'0.65':[21,22],'1.0':[21,22],'1.5':[21,22],'2.5':[21,22],'4.0':[21,22],'6.5':[21,22],'10.0':[21,22] }, 'R': { '0.065':[7,8],'0.10':[10,11],'0.15':[14,15],'0.25':[21,22],'0.40':[21,22],'0.65':[21,22],'1.0':[21,22],'1.5':[21,22],'2.5':[21,22],'4.0':[21,22],'6.5':[21,22],'10.0':[21,22] } };
// Tightened inspection (Table II-B) — stricter Ac/Re numbers const tightenedTable = { 'A': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null,'0.65':null,'0.10':null, '1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[0,1],'6.5':[0,1],'10.0':[0,1] }, 'B': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null,'0.65':null, '1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[0,1],'6.5':[0,1],'10.0':[0,1] }, 'C': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null, '0.65':[0,1],'1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[0,1],'6.5':[1,2],'10.0':[1,2] }, 'D': { '0.065':null,'0.10':null,'0.15':null,'0.25':null, '0.40':[0,1],'0.65':[0,1],'1.0':[0,1],'1.5':[0,1],'2.5':[1,2],'4.0':[1,2],'6.5':[2,3],'10.0':[3,4] }, 'E': { '0.065':null,'0.10':null,'0.15':null, '0.25':[0,1],'0.40':[0,1],'0.65':[0,1],'1.0':[0,1],'1.5':[1,2],'2.5':[2,3],'4.0':[3,4],'6.5':[5,6],'10.0':[5,6] }, 'F': { '0.065':null,'0.10':null, '0.15':[0,1],'0.25':[0,1],'0.40':[0,1],'0.65':[0,1],'1.0':[1,2],'1.5':[2,3],'2.5':[3,4],'4.0':[5,6],'6.5':[5,6],'10.0':[8,9] }, 'G': { '0.065':null, '0.10':[0,1],'0.15':[0,1],'0.25':[0,1],'0.40':[0,1],'0.65':[1,2],'1.0':[2,3],'1.5':[3,4],'2.5':[5,6],'4.0':[5,6],'6.5':[8,9],'10.0':[12,13] }, 'H': { '0.065':[0,1],'0.10':[0,1],'0.15':[0,1],'0.25':[0,1],'0.40':[1,2],'0.65':[2,3],'1.0':[3,4],'1.5':[5,6],'2.5':[5,6],'4.0':[8,9],'6.5':[12,13],'10.0':[18,19] }, 'J': { '0.065':[0,1],'0.10':[0,1],'0.15':[0,1],'0.25':[1,2],'0.40':[2,3],'0.65':[3,4],'1.0':[5,6],'1.5':[5,6],'2.5':[8,9],'4.0':[12,13],'6.5':[18,19],'10.0':[18,19] }, 'K': { '0.065':[0,1],'0.10':[0,1],'0.15':[1,2],'0.25':[2,3],'0.40':[3,4],'0.65':[5,6],'1.0':[5,6],'1.5':[8,9],'2.5':[12,13],'4.0':[18,19],'6.5':[18,19],'10.0':[18,19] }, 'L': { '0.065':[0,1],'0.10':[1,2],'0.15':[2,3],'0.25':[3,4],'0.40':[5,6],'0.65':[5,6],'1.0':[8,9],'1.5':[12,13],'2.5':[18,19],'4.0':[18,19],'6.5':[18,19],'10.0':[18,19] }, 'M': { '0.065':[1,2],'0.10':[2,3],'0.15':[3,4],'0.25':[5,6],'0.40':[5,6],'0.65':[8,9],'1.0':[12,13],'1.5':[18,19],'2.5':[18,19],'4.0':[18,19],'6.5':[18,19],'10.0':[18,19] }, 'N': { '0.065':[2,3],'0.10':[3,4],'0.15':[5,6],'0.25':[5,6],'0.40':[8,9],'0.65':[12,13],'1.0':[18,19],'1.5':[18,19],'2.5':[18,19],'4.0':[18,19],'6.5':[18,19],'10.0':[18,19] }, 'P': { '0.065':[3,4],'0.10':[5,6],'0.15':[5,6],'0.25':[8,9],'0.40':[12,13],'0.65':[18,19],'1.0':[18,19],'1.5':[18,19],'2.5':[18,19],'4.0':[18,19],'6.5':[18,19],'10.0':[18,19] }, 'Q': { '0.065':[5,6],'0.10':[5,6],'0.15':[8,9],'0.25':[12,13],'0.40':[18,19],'0.65':[18,19],'1.0':[18,19],'1.5':[18,19],'2.5':[18,19],'4.0':[18,19],'6.5':[18,19],'10.0':[18,19] }, 'R': { '0.065':[5,6],'0.10':[8,9],'0.15':[12,13],'0.25':[18,19],'0.40':[18,19],'0.65':[18,19],'1.0':[18,19],'1.5':[18,19],'2.5':[18,19],'4.0':[18,19],'6.5':[18,19],'10.0':[18,19] } };
// Reduced inspection (Table II-C) — smaller sample sizes, different Ac/Re const reducedTable = { 'A': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null,'0.65':null, '1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[0,1],'6.5':[0,1],'10.0':[0,1] }, 'B': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null,'0.65':null, '1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[0,1],'6.5':[0,1],'10.0':[0,1] }, 'C': { '0.065':null,'0.10':null,'0.15':null,'0.25':null,'0.40':null, '0.65':[0,1],'1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[0,1],'6.5':[0,1],'10.0':[1,2] }, 'D': { '0.065':null,'0.10':null,'0.15':null,'0.25':null, '0.40':[0,1],'0.65':[0,1],'1.0':[0,1],'1.5':[0,1],'2.5':[0,1],'4.0':[1,2],'6.5':[1,2],'10.0':[2,3] }, 'E': { '0.065':null,'0.10':null,'0.15':null, '0.25':[0,1],'0.40':[0,1],'0.65':[0,1],'1.0':[0,1],'1.5':[1,2],'2.5':[1,2],'4.0':[2,3],'6.5':[3,4],'10.0':[5,6] }, 'F': { '0.065':null,'0.10':null, '0.15':[0,1],'0.25':[0,1],'0.40':[0,1],'0.65':[0,1],'1.0':[1,2],'1.5':[1,2],'2.5':[2,3],'4.0':[3,4],'6.5':[5,6],'10.0':[7,8] }, 'G': { '0.065':null, '0.10':[0,1],'0.15':[0,1],'0.25':[0,1],'0.40':[0,1],'0.65':[1,2],'1.0':[1,2],'1.5':[2,3],'2.5':[3,4],'4.0':[5,6],'6.5':[7,8],'10.0':[10,11] }, 'H': { '0.065':[0,1],'0.10':[0,1],'0.15':[0,1],'0.25':[0,1],'0.40':[1,2],'0.65':[1,2],'1.0':[2,3],'1.5':[3,4],'2.5':[5,6],'4.0':[7,8],'6.5':[10,11],'10.0':[14,15] }, 'J': { '0.065':[0,1],'0.10':[0,1],'0.15':[0,1],'0.25':[1,2],'0.40':[1,2],'0.65':[2,3],'1.0':[3,4],'1.5':[5,6],'2.5':[7,8],'4.0':[10,11],'6.5':[14,15],'10.0':[14,15] }, 'K': { '0.065':[0,1],'0.10':[0,1],'0.15':[1,2],'0.25':[1,2],'0.40':[2,3],'0.65':[3,4],'1.0':[5,6],'1.5':[7,8],'2.5':[10,11],'4.0':[14,15],'6.5':[14,15],'10.0':[14,15] }, 'L': { '0.065':[0,1],'0.10':[1,2],'0.15':[1,2],'0.25':[2,3],'0.40':[3,4],'0.65':[5,6],'1.0':[7,8],'1.5':[10,11],'2.5':[14,15],'4.0':[14,15],'6.5':[14,15],'10.0':[14,15] }, 'M': { '0.065':[1,2],'0.10':[1,2],'0.15':[2,3],'0.25':[3,4],'0.40':[5,6],'0.65':[7,8],'1.0':[10,11],'1.5':[14,15],'2.5':[14,15],'4.0':[14,15],'6.5':[14,15],'10.0':[14,15] }, 'N': { '0.065':[1,2],'0.10':[2,3],'0.15':[3,4],'0.25':[5,6],'0.40':[7,8],'0.65':[10,11],'1.0':[14,15],'1.5':[14,15],'2.5':[14,15],'4.0':[14,15],'6.5':[14,15],'10.0':[14,15] }, 'P': { '0.065':[2,3],'0.10':[3,4],'0.15':[5,6],'0.25':[7,8],'0.40':[10,11],'0.65':[14,15],'1.0':[14,15],'1.5':[14,15],'2.5':[14,15],'4.0':[14,15],'6.5':[14,15],'10.0':[14,15] }, 'Q': { '0.065':[3,4],'0.10':[5,6],'0.15':[7,8],'0.25':[10,11],'0.40':[14,15],'0.65':[14,15],'1.0':[14,15],'1.5':[14,15],'2.5':[14,15],'4.0':[14,15],'6.5':[14,15],'10.0':[14,15] }, 'R': { '0.065':[5,6],'0.10':[7,8],'0.15':[10,11],'0.25':[14,15],'0.40':[14,15],'0.65':[14,15],'1.0':[14,15],'1.5':[14,15],'2.5':[14,15],'4.0':[14,15],'6.5':[14,15],'10.0':[14,15] } };
// Code letter order for arrow resolution const codeOrder = ['A','B','C','D','E','F','G','H','J','K','L','M','N','P','Q','R'];
// Step 1: Find code letter let codeLetter = null; const levelIndex = {'I': 2, 'II': 3, 'III': 4}; const colIdx = levelIndex[inspLevel]; for (let row of lotSizeTable) { if (lotSize >= row[0] && lotSize Lot size out of supported range (2 – 500,000+).'; return; }
// Step 2: Select table let table = normalTable; if (inspType === 'tightened') table = tightenedTable; else if (inspType === 'reduced') table = reducedTable;
// Step 3: Look up Ac/Re, resolve arrows (null = use next code letter up) const aqlKey = String(aql); let resolvedCode = codeLetter; let acRe = null; let arrowUp = false; let arrowDown = false;
// Try current code, then walk up (larger sample) if null let idx = codeOrder.indexOf(codeLetter); while (idx No sampling plan available for this AQL at the selected code letter. Try a higher AQL or different inspection level.'; return; }
const sampleSize = sampleSizeMap[resolvedCode]; const ac = acRe[0]; const re = acRe[1];
// Step 4: Compute estimated defect rate context const maxDefects = Math.round(lotSize * aql / 100); const percentSampled = ((sampleSize / lotSize) * 100).toFixed(1);
// Step 5: Consumer Risk (Beta) approximation using Poisson // P(accept | true defect rate p) = sum_{k=0}^{Ac} e^{-np} * (np)^k / k! function poissonCDF(lambda, k) { let sum = 0; let term = Math.exp(-lambda); sum += term; for (let i = 1; i
Lot Size (N) ${lotSize.toLocaleString()}
Inspection Level Level ${inspLevel} — ${inspType.charAt(0).toUpperCase()+inspType.slice(1)}
Sample Size Code Letter ${resolvedCode}
Sample Size (n) ${sampleSize}
AQL (%) ${aql}%
Acceptance Number (Ac) ${ac}
Rejection Number (Re) ${re}
% of Lot Sampled ${percentSampled}%
Max Allowable Defects in Lot ${maxDefects.toLocaleString()}
Producer Risk α (at AQL) ${producerRisk}%
Consumer Risk β (at RQL ≈ ${rql}%) ${consumerRisk}%
Decision Rule: Inspect ${sampleSize} units from the lot. If defects found ≤ ${ac} → ACCEPT the lot. If defects found ≥ ${re} → REJECT the lot. `; }
#### Formula & Method
This calculator implements ANSI/ASQ Z1.4 (ISO 2859-1) single-sampling plans for attributes.
Step 1 — Find Sample Size Code Letter: Use Table I of ANSI/ASQ Z1.4 with the lot size N and chosen General Inspection Level (I, II, or III) to obtain a code letter (A–R).
Step 2 — Find Sample Size n and Ac/Re: Use Table II-A (Normal), II-B (Tightened), or II-C (Reduced) with the code letter and AQL to obtain: • n = sample size • Ac = acceptance number (max defects to accept lot) • Re = rejection number = Ac + 1
Step 3 — Arrow Rule: If no plan exists at the intersection, follow the arrow: ↓ use the first plan below (larger sample size).
Producer Risk (α): P(reject | p = AQL) = 1 − P(X ≤ Ac | λ = n × AQL) where X ~ Poisson(λ). Typically α ≈ 5%.
Consumer Risk (β): P(accept | p = RQL) = P(X ≤ Ac | λ = n × RQL) RQL (Rejectable Quality Level) ≈ 10 × AQL. Typically β ≈ 10%.
Max Allowable Defects in Lot: = floor(N × AQL / 100)
#### Assumptions & References
- Based on ANSI/ASQ Z1.4-2008 (equivalent to ISO 2859-1) — the international standard for attribute sampling inspection.
- Applies to single-sampling plans only (not double or multiple sampling).
- Level I is used when less discrimination is needed (smaller samples); Level II is the default; Level III provides greater discrimination (larger samples).
- Normal inspection is the default. Switch to Tightened after 2 of 5 consecutive lots are rejected; switch to Reduced after 10 consecutive lots accepted under normal inspection.
- Producer Risk (α) and Consumer Risk (β) are approximated using the Poisson distribution, which is valid when n is large and p is small (np < 5 rule of thumb).
- Reference: ANSI/ASQ Z1.4-2008, Sampling Procedures and Tables for Inspection by Attributes, ASQ Quality Press.
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