{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,17]],"date-time":"2026-03-17T08:24:50Z","timestamp":1773735890471,"version":"3.50.1"},"reference-count":20,"publisher":"Wiley","issue":"12","license":[{"start":{"date-parts":[[2006,11,2]],"date-time":"2006-11-02T00:00:00Z","timestamp":1162425600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Statistics in Medicine"],"published-print":{"date-parts":[[2007,5,30]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>In clinical trials with <jats:italic>t<\/jats:italic>\u2010distributed test statistics the required sample size depends on the unknown variance. Taking estimates from previous studies often leads to a misspecification of the true value of the variance. Hence, re\u2010estimation of the variance based on the collected data and re\u2010calculation of the required sample size is attractive. We present a flexible method for extensions of fixed sample or group\u2010sequential trials with <jats:italic>t<\/jats:italic>\u2010distributed test statistics. The method can be applied at any time during the course of the trial and does not require the necessity to pre\u2010specify a sample size re\u2010calculation rule. All available information can be used to determine the new sample size. The advantage of our method when compared with other adaptive methods is maintenance of the efficient <jats:italic>t<\/jats:italic>\u2010test design when no extensions are actually made. We show that the type I error rate is preserved. Copyright \u00a9 2006 John Wiley &amp; Sons, Ltd.<\/jats:p>","DOI":"10.1002\/sim.2725","type":"journal-article","created":{"date-parts":[[2006,11,2]],"date-time":"2006-11-02T10:09:04Z","timestamp":1162462144000},"page":"2449-2464","source":"Crossref","is-referenced-by-count":18,"title":["Increasing the sample size during clinical trials with <i>t<\/i>\u2010distributed test statistics without inflating the type I error rate"],"prefix":"10.1002","volume":"26","author":[{"given":"Nina","family":"Timmesfeld","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Helmut","family":"Sch\u00e4fer","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hans\u2010Helge","family":"M\u00fcller","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2007,4,13]]},"reference":[{"key":"e_1_2_1_2_2","doi-asserted-by":"publisher","DOI":"10.1214\/aoms\/1177731088"},{"key":"e_1_2_1_3_2","doi-asserted-by":"publisher","DOI":"10.1002\/sim.4780090113"},{"key":"e_1_2_1_4_2","doi-asserted-by":"publisher","DOI":"10.1002\/sim.4780132309"},{"key":"e_1_2_1_5_2","doi-asserted-by":"publisher","DOI":"10.1002\/(SICI)1097-0258(20000415)19:7<901::AID-SIM405>3.0.CO;2-L"},{"key":"e_1_2_1_6_2","doi-asserted-by":"publisher","DOI":"10.1002\/(SICI)1097-0258(19990715)18:13<1575::AID-SIM153>3.0.CO;2-Z"},{"key":"e_1_2_1_7_2","doi-asserted-by":"publisher","DOI":"10.1093\/biomet\/87.1.125"},{"key":"e_1_2_1_8_2","first-page":"130","article-title":"Multistage testing with adaptive designs (with discussion)","volume":"20","author":"Bauer P","year":"1989","journal-title":"Biometrie und Informatik in Medizin und Biologie"},{"key":"e_1_2_1_9_2","doi-asserted-by":"publisher","DOI":"10.2307\/2533441"},{"key":"e_1_2_1_10_2","doi-asserted-by":"publisher","DOI":"10.2307\/2533262"},{"key":"e_1_2_1_11_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.0006-341X.1999.01286.x"},{"key":"e_1_2_1_12_2","doi-asserted-by":"publisher","DOI":"10.1198\/016214502753479374"},{"key":"e_1_2_1_13_2","doi-asserted-by":"publisher","DOI":"10.1002\/sim.734"},{"key":"e_1_2_1_14_2","doi-asserted-by":"publisher","DOI":"10.1177\/009286150103500407"},{"key":"e_1_2_1_15_2","doi-asserted-by":"publisher","DOI":"10.1002\/sim.1852"},{"key":"e_1_2_1_16_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.0006\u2010341X.2001.00886.x"},{"key":"e_1_2_1_17_2","doi-asserted-by":"publisher","DOI":"10.1002\/sim.1136"},{"key":"e_1_2_1_18_2","doi-asserted-by":"publisher","DOI":"10.1002\/bimj.200410042"},{"key":"e_1_2_1_19_2","series-title":"Springer Texts in Statistics","volume-title":"Testing Statistical Hypotheses","author":"Lehmann EL","year":"2005"},{"issue":"1","key":"e_1_2_1_20_2","first-page":"133","article-title":"Exact calculations for sequential t, \u03c72 and F tests","volume":"78","author":"Jennison C","year":"1991","journal-title":"Biometrika"},{"key":"e_1_2_1_21_2","unstructured":"R Development Core Team. 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