Knowledge

Probability integral transform

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is to provide the basis for testing whether a set of observations can reasonably be modelled as arising from a specified distribution. Specifically, the probability integral transform is applied to construct an equivalent set of values, and a test is then made of whether a uniform distribution is
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for a set of random variables is simplified or reduced in apparent complexity by applying the probability integral transform to each of the components and then working with a joint distribution for which the marginal variables have uniform distributions.
1342: 836:{\displaystyle {\begin{aligned}F_{Y}(y)&=\operatorname {P} (Y\leq y)\\&=\operatorname {P} (F_{X}(X)\leq y)\\&=\operatorname {P} (X\leq F_{X}^{-1}(y))\\&=F_{X}(F_{X}^{-1}(y))\\&=y\end{aligned}}} 43:. This holds exactly provided that the distribution being used is the true distribution of the random variables; if the distribution is one fitted to the data, the result will hold approximately in large samples. 1053: 611: 99:
A third use is based on applying the inverse of the probability integral transform to convert random variables from a uniform distribution to have a selected distribution: this is known as
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The result is sometimes modified or extended so that the result of the transformation is a standard distribution other than the uniform distribution, such as the
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which are a means of both defining and working with distributions for statistically dependent multivariate data. Here the problem of defining or manipulating a
1267: 298: 1526:{\displaystyle \Phi (x)={\frac {1}{\sqrt {2\pi }}}\int _{-\infty }^{x}{\rm {e}}^{-t^{2}/2}\,{\rm {d}}t={\frac {1}{2}}{\Big },\quad x\in \mathbb {R} ,\,} 1931: 59: 40: 986: 136: 92: 1539: 1165: 242: 348: 1300: 81: 1834: 913: 100: 1666: 951: 195: 1657: 849: 497: 47: 1731: 1598: 323: 1860: 132: 36: 1784: 1096: 1058: 561: 417: 142: 1138: 893: 459: 251: 8: 343: 88: 1575: 1893: 1874:"The Probability Integral Transformation When Parameters are Estimated from the Sample" 1639: 1280: 1220: 541: 397: 303: 172: 114: 20: 1240: 271: 1885: 32: 1778:
has a uniform distribution. Moreover, by symmetry of the uniform distribution,
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and the immediate result of the probability integral transform is that
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does not exist, then it can be replaced in this proof by the function
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A second use for the transformation is in the theory related to
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appropriate for the constructed dataset. Examples of this are
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One use for the probability integral transform in statistical
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be a random variable with a standard normal distribution
1048:{\displaystyle \chi (y)\equiv \inf\{x:F_{X}(x)\geq y\}} 1787: 1734: 1669: 1642: 1601: 1578: 1542: 1345: 1303: 1283: 1243: 1223: 1168: 1141: 1099: 1061: 989: 954: 916: 896: 852: 609: 564: 544: 500: 462: 420: 400: 351: 326: 306: 274: 254: 198: 175: 145: 117: 1814: 1767: 1714: 1648: 1625: 1587: 1560: 1525: 1328: 1289: 1261: 1229: 1209: 1154: 1127: 1085: 1047: 975: 940: 902: 882: 835: 592: 550: 530: 486: 448: 406: 378: 334: 312: 292: 260: 230: 181: 161: 123: 1499: 1491: 1472: 1452: 1923: 1005: 39:can be converted to random variables having a 1910: 1871: 1042: 1008: 1237:has a uniform distribution on the interval 1911:Casella, George; Berger, Roger L. (2002). 1857:The Oxford Dictionary of Statistical Terms 1522: 1515: 1496: 1457: 1426: 328: 224: 60:Statistical Methods for Research Workers 1851: 1849: 1561:{\displaystyle \operatorname {erf} (),} 1277:For a first, illustrative example, let 1210:{\displaystyle \mathrm {Uniform} (0,1)} 538:exists (i.e., if there exists a unique 1924: 137:cumulative distribution function (CDF) 1915:(2nd ed.). Theorem 2.1.10, p.54. 1872:David, F. N.; Johnson, N. L. (1948). 394:Given any random continuous variable 1846: 379:{\displaystyle \mu \circ F_{X}^{-1}} 1932:Theory of probability distributions 1329:{\displaystyle {\mathcal {N}}(0,1)} 13: 1608: 1429: 1397: 1384: 1346: 1306: 1188: 1185: 1182: 1179: 1176: 1173: 1170: 970: 935: 718: 671: 640: 14: 1943: 1825:also has a uniform distribution. 1660:with unit mean, then its CDF is 941:{\displaystyle \chi (0)=-\infty } 1715:{\displaystyle F(x)=1-\exp(-x),} 976:{\displaystyle \chi (1)=\infty } 57:in his 1932 edition of the book 53:The transform was introduced by 1572:. Then the new random variable 1507: 111:Suppose that a random variable 66: 1904: 1865: 1809: 1800: 1762: 1753: 1706: 1697: 1679: 1673: 1617: 1611: 1552: 1549: 1355: 1349: 1323: 1311: 1256: 1244: 1204: 1192: 1116: 1110: 1080: 1068: 1033: 1027: 999: 993: 964: 958: 926: 920: 877: 871: 813: 810: 804: 783: 760: 757: 751: 724: 705: 696: 690: 677: 658: 646: 630: 624: 581: 575: 525: 519: 481: 469: 443: 437: 287: 275: 231:{\displaystyle Y:=F_{X}(X)\,,} 221: 215: 93:joint probability distribution 25:probability integral transform 1: 1840: 883:{\displaystyle F_{X}^{-1}(y)} 531:{\displaystyle F_{X}^{-1}(y)} 243:standard uniform distribution 41:standard uniform distribution 1768:{\displaystyle Y=1-\exp(-X)} 1626:{\displaystyle Y:=\Phi (X),} 1093:, with the same result that 335:{\displaystyle \mathbb {R} } 106: 16:Probability theory operation 7: 1828: 1272: 29:universality of the uniform 10: 1948: 1835:Inverse transform sampling 1815:{\displaystyle Z=\exp(-X)} 1633:is uniformly distributed. 1128:{\displaystyle F_{Y}(y)=y} 1086:{\displaystyle y\in (0,1)} 593:{\displaystyle F_{X}(x)=y} 449:{\displaystyle Y=F_{X}(X)} 268:is the uniform measure on 101:inverse transform sampling 1217:random variable, so that 169:Then the random variable 1658:exponential distribution 389: 82:Kolmogorov–Smirnov tests 48:exponential distribution 1861:Oxford University Press 133:continuous distribution 37:continuous distribution 1816: 1769: 1716: 1650: 1636:As second example, if 1627: 1589: 1562: 1527: 1330: 1291: 1263: 1231: 1211: 1156: 1129: 1087: 1049: 977: 942: 904: 884: 837: 594: 552: 532: 488: 450: 408: 380: 336: 314: 300:, the distribution of 294: 262: 232: 183: 163: 162:{\displaystyle F_{X}.} 125: 1913:Statistical Inference 1817: 1770: 1717: 1651: 1628: 1590: 1563: 1528: 1331: 1292: 1264: 1232: 1212: 1162:is just the CDF of a 1157: 1155:{\displaystyle F_{Y}} 1130: 1088: 1050: 978: 943: 905: 903:{\displaystyle \chi } 885: 838: 595: 553: 533: 489: 487:{\displaystyle y\in } 451: 409: 381: 337: 315: 295: 263: 233: 184: 164: 126: 1785: 1732: 1667: 1640: 1599: 1576: 1540: 1343: 1301: 1281: 1241: 1221: 1166: 1139: 1097: 1059: 987: 952: 914: 894: 850: 607: 562: 542: 498: 460: 418: 398: 349: 324: 304: 272: 261:{\displaystyle \mu } 252: 196: 173: 143: 115: 1393: 870: 803: 750: 518: 375: 344:pushforward measure 1812: 1765: 1712: 1646: 1623: 1588:{\displaystyle Y,} 1585: 1558: 1523: 1376: 1336:. Then its CDF is 1326: 1287: 1259: 1227: 1207: 1152: 1125: 1083: 1045: 973: 938: 910:, where we define 900: 880: 853: 833: 831: 786: 733: 590: 548: 528: 501: 484: 446: 404: 376: 358: 332: 310: 290: 258: 228: 179: 159: 121: 21:probability theory 1855:Dodge, Y. (2006) 1649:{\displaystyle X} 1487: 1486: 1448: 1374: 1373: 1290:{\displaystyle X} 1230:{\displaystyle Y} 551:{\displaystyle x} 407:{\displaystyle X} 313:{\displaystyle X} 248:Equivalently, if 182:{\displaystyle Y} 124:{\displaystyle X} 1939: 1917: 1916: 1908: 1902: 1901: 1869: 1863: 1853: 1821: 1819: 1818: 1813: 1774: 1772: 1771: 1766: 1721: 1719: 1718: 1713: 1655: 1653: 1652: 1647: 1632: 1630: 1629: 1624: 1594: 1592: 1591: 1586: 1567: 1565: 1564: 1559: 1532: 1530: 1529: 1524: 1518: 1503: 1502: 1495: 1494: 1488: 1482: 1478: 1476: 1475: 1456: 1455: 1449: 1441: 1433: 1432: 1425: 1424: 1420: 1415: 1414: 1401: 1400: 1392: 1387: 1375: 1366: 1362: 1335: 1333: 1332: 1327: 1310: 1309: 1296: 1294: 1293: 1288: 1268: 1266: 1265: 1262:{\displaystyle } 1260: 1236: 1234: 1233: 1228: 1216: 1214: 1213: 1208: 1191: 1161: 1159: 1158: 1153: 1151: 1150: 1134: 1132: 1131: 1126: 1109: 1108: 1092: 1090: 1089: 1084: 1054: 1052: 1051: 1046: 1026: 1025: 982: 980: 979: 974: 947: 945: 944: 939: 909: 907: 906: 901: 889: 887: 886: 881: 869: 861: 842: 840: 839: 834: 832: 819: 802: 794: 782: 781: 766: 749: 741: 711: 689: 688: 664: 623: 622: 599: 597: 596: 591: 574: 573: 557: 555: 554: 549: 537: 535: 534: 529: 517: 509: 493: 491: 490: 485: 455: 453: 452: 447: 436: 435: 413: 411: 410: 405: 385: 383: 382: 377: 374: 366: 341: 339: 338: 333: 331: 319: 317: 316: 311: 299: 297: 296: 293:{\displaystyle } 291: 267: 265: 264: 259: 237: 235: 234: 229: 214: 213: 188: 186: 185: 180: 168: 166: 165: 160: 155: 154: 130: 128: 127: 122: 33:random variables 1947: 1946: 1942: 1941: 1940: 1938: 1937: 1936: 1922: 1921: 1920: 1909: 1905: 1890:10.2307/2332638 1870: 1866: 1854: 1847: 1843: 1831: 1786: 1783: 1782: 1733: 1730: 1729: 1668: 1665: 1664: 1641: 1638: 1637: 1600: 1597: 1596: 1577: 1574: 1573: 1541: 1538: 1537: 1514: 1498: 1497: 1490: 1489: 1477: 1471: 1470: 1451: 1450: 1440: 1428: 1427: 1416: 1410: 1406: 1402: 1396: 1395: 1394: 1388: 1380: 1361: 1344: 1341: 1340: 1305: 1304: 1302: 1299: 1298: 1282: 1279: 1278: 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1687: 1684: 1681: 1678: 1675: 1672: 1645: 1622: 1619: 1616: 1613: 1610: 1607: 1604: 1584: 1581: 1570:error function 1557: 1554: 1551: 1548: 1545: 1534: 1533: 1521: 1517: 1513: 1510: 1506: 1501: 1493: 1485: 1481: 1474: 1469: 1466: 1463: 1460: 1454: 1447: 1444: 1439: 1436: 1431: 1423: 1419: 1413: 1409: 1405: 1399: 1391: 1386: 1383: 1379: 1372: 1369: 1365: 1360: 1357: 1354: 1351: 1348: 1325: 1322: 1319: 1316: 1313: 1308: 1286: 1274: 1271: 1258: 1255: 1252: 1249: 1246: 1226: 1206: 1203: 1200: 1197: 1194: 1190: 1187: 1184: 1181: 1178: 1175: 1172: 1149: 1145: 1124: 1121: 1118: 1115: 1112: 1107: 1103: 1082: 1079: 1076: 1073: 1070: 1067: 1064: 1044: 1041: 1038: 1035: 1032: 1029: 1024: 1020: 1016: 1013: 1010: 1007: 1004: 1001: 998: 995: 992: 972: 969: 966: 963: 960: 957: 937: 934: 931: 928: 925: 922: 919: 899: 879: 876: 873: 868: 865: 860: 856: 844: 843: 828: 825: 822: 820: 818: 815: 812: 809: 806: 801: 798: 793: 789: 785: 780: 776: 772: 769: 767: 765: 762: 759: 756: 753: 748: 745: 740: 736: 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51: 49: 44: 42: 38: 34: 30: 26: 22: 1912: 1906: 1884:(1/2): 182. 1881: 1877: 1867: 1856: 1824: 1777: 1724: 1635: 1535: 1276: 845: 393: 247: 240: 110: 98: 86: 70: 67:Applications 58: 52: 45: 28: 24: 18: 1595:defined by 189:defined as 1878:Biometrika 1841:References 558:such that 1804:− 1798:⁡ 1757:− 1751:⁡ 1745:− 1701:− 1695:⁡ 1689:− 1609:Φ 1547:⁡ 1512:∈ 1468:⁡ 1404:− 1385:∞ 1382:− 1378:∫ 1371:π 1347:Φ 1066:∈ 1037:≥ 1003:≡ 991:χ 971:∞ 956:χ 936:∞ 933:− 918:χ 898:χ 864:− 797:− 744:− 731:≤ 722:⁡ 700:≤ 675:⁡ 653:≤ 644:⁡ 600:), then: 512:− 467:∈ 414:, define 369:− 356:∘ 353:μ 256:μ 107:Statement 78:P–P plots 1926:Category 1829:See also 1273:Examples 1135:. Thus, 456:. Given 1898:2332638 1656:has an 1568:is the 342:is the 89:copulas 1896:  1536:where 983:, and 241:has a 131:has a 23:, the 1894:JSTOR 494:, if 390:Proof 1055:for 80:and 1886:doi 1795:exp 1748:exp 1692:exp 1544:erf 1465:erf 1006:inf 846:If 320:on 139:is 19:In 1928:: 1892:. 1882:35 1880:. 1876:. 1859:, 1848:^ 1606::= 1269:. 948:, 386:. 245:. 203::= 103:. 84:. 63:. 50:. 1900:. 1888:: 1810:) 1807:X 1801:( 1792:= 1789:Z 1763:) 1760:X 1754:( 1742:1 1739:= 1736:Y 1710:, 1707:) 1704:x 1698:( 1686:1 1683:= 1680:) 1677:x 1674:( 1671:F 1644:X 1621:, 1618:) 1615:X 1612:( 1603:Y 1583:, 1580:Y 1556:, 1553:) 1550:( 1520:, 1516:R 1509:x 1505:, 1500:] 1492:) 1484:2 1480:x 1473:( 1462:+ 1459:1 1453:[ 1446:2 1443:1 1438:= 1435:t 1430:d 1422:2 1418:/ 1412:2 1408:t 1398:e 1390:x 1368:2 1364:1 1359:= 1356:) 1353:x 1350:( 1324:) 1321:1 1318:, 1315:0 1312:( 1307:N 1285:X 1257:] 1254:1 1251:, 1248:0 1245:[ 1225:Y 1205:) 1202:1 1199:, 1196:0 1193:( 1189:m 1186:r 1183:o 1180:f 1177:i 1174:n 1171:U 1148:Y 1144:F 1123:y 1120:= 1117:) 1114:y 1111:( 1106:Y 1102:F 1081:) 1078:1 1075:, 1072:0 1069:( 1063:y 1043:} 1040:y 1034:) 1031:x 1028:( 1023:X 1019:F 1015:: 1012:x 1009:{ 1000:) 997:y 994:( 968:= 965:) 962:1 959:( 930:= 927:) 924:0 921:( 878:) 875:y 872:( 867:1 859:X 855:F 827:y 824:= 814:) 811:) 808:y 805:( 800:1 792:X 788:F 784:( 779:X 775:F 771:= 761:) 758:) 755:y 752:( 747:1 739:X 735:F 728:X 725:( 719:P 716:= 706:) 703:y 697:) 694:X 691:( 686:X 682:F 678:( 672:P 669:= 659:) 656:y 650:Y 647:( 641:P 638:= 631:) 628:y 625:( 620:Y 616:F 588:y 585:= 582:) 579:x 576:( 571:X 567:F 546:x 526:) 523:y 520:( 515:1 507:X 503:F 482:] 479:1 476:, 473:0 470:[ 464:y 444:) 441:X 438:( 433:X 429:F 425:= 422:Y 402:X 372:1 364:X 360:F 329:R 308:X 288:] 285:1 282:, 279:0 276:[ 226:, 222:) 219:X 216:( 211:X 207:F 200:Y 177:Y 157:. 152:X 148:F 119:X

Index

probability theory
random variables
continuous distribution
standard uniform distribution
exponential distribution
Ronald Fisher
Statistical Methods for Research Workers
data analysis
P–P plots
Kolmogorov–Smirnov tests
copulas
joint probability distribution
inverse transform sampling
continuous distribution
cumulative distribution function (CDF)
standard uniform distribution
pushforward measure
error function
exponential distribution
Inverse transform sampling


Oxford University Press
"The Probability Integral Transformation When Parameters are Estimated from the Sample"
doi
10.2307/2332638
JSTOR
2332638
Category
Theory of probability distributions

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