![\"\"](\"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/5\/51\/Mandatory_road_sign_stop.svg\/600px-Mandatory_road_sign_stop.svg.png\")
If you were cycling or driving, you’d probably know what the stopping rules were. Traffic not moving, big red sign, large goose with malevolent glare (Lincolnshire speciality).<\/p>\nIf you were cycling or driving, you’d probably know what the stopping rules were. Traffic not moving, big red sign, large goose with malevolent glare (Lincolnshire speciality).<\/p>\n
What if you’re doing a clinical trial?<\/p>\n
There are a variety of things what have been described, some of them are qualitative (SUSAR – sudden, unexpected, serious adverse reactions) and some statistical. The latter have with them a set of maths that leads to reasons to discontinue, either for proven benefit or futility.<\/p>\n
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The maths is argued over by clever people, but they all conceptually do the same thing. They ask “what is the likelihood of this difference being a chance finding?” and balance this with “and if we keep looking and looking, eventually we will see something”.<\/p>\n
This means that the trial designers need to decide what their significance level and power<\/a> are that they are aiming for, their minimally clinically important difference<\/a>\u00a0and then how many times they are going to look<\/a>. (The simplest idea is that if you look twice, you have to halve the p-value you’re going to accept as significant, cause you’ve used up one lot of assessing.) This then produces a size estimation for the study and\u00a0boundaries for “better – stop!” and “futile – stop!” at each reassessment.<\/p>\n The usual maths\u00a0of doing this is with the ‘Flemming-O’Brien alpha spending function’, but a more efficient variant is the Triangular Test, which recalibrates as it ammasses data.<\/p>\n – Archi<\/p>\n (PS – This post was requested by – You can ask too!)<\/p>\n @drbobphillips<\/a> can you do a blog piece on ‘triangular test?’ Google not helping. Authors closed study because of results of this? ?<\/p>\n \u2014 XOXO \u0628\u0646\u062a \u0627\u0644\u0642\u064a\u0644 (@hhassan90210) July 13, 2015<\/a><\/p><\/blockquote>\n <\/p>\n <\/p>\n (If you want a longer & more intellectual read – try here<\/a>.)<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" If you were cycling or driving, you’d probably know what the stopping rules were. Traffic not moving, big red sign, large goose with malevolent glare (Lincolnshire speciality). What if you’re doing a clinical trial? There are a variety of things what have been described, some of them are qualitative (SUSAR – sudden, unexpected, serious adverse […]<\/p>\n![\"\"](\"http:\/\/lh6.ggpht.com\/_1wtadqGaaPs\/THaQHGSn6GI\/AAAAAAAAWGg\/LwPoRDFbQCk\/tmp3A8370_thumb_thumb.png?imgmax=800\")
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