235:-value threshold is the same at each interim analysis. The disadvantages are that the number of interim analyses must be fixed at the start and it is not possible under this scheme to add analyses after the trial has started. Another disadvantage is that investigators and readers frequently do not understand how the
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or conventional treatment, while the other group of patients are given the treatment that is being tested. The investigators running the clinical trial will wish to stop the trial early for ethical reasons if the treatment group clearly shows evidence of benefit. In other words, "when early results
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threshold for each interim analysis which guides the data monitoring committee on whether to stop the trial. The boundary used depends on the number of interim analyses.
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239:-values are reported: for example, if there are five interim analyses planned, but the trial is stopped after the third interim analysis because the
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proved so promising it was no longer fair to keep patients on the older drugs for comparison, without giving them the opportunity to change."
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in 1977. The many reasons underlying when to stop a clinical trial for benefit were discussed in his editorial from 2005.
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343:(1977). "Group sequential methods in the design and analysis of clinical trials".
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380:"Multiplicity in randomised trials II: subgroup and interim analyses"
247:-value for the trial is still reported as <0.05 and not as 0.01.
63:-values used at each interim analysis, assuming the overall
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The concept was introduced by the medical statistician
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compares two groups of patients. One group are given a
300:"When (not) to stop a clinical trial for benefit"
231:The Pocock boundary is simple to use in that the
20:is a method for determining whether to stop a
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278:"Heart attacks may be cut by half"
243:-value was 0.01, then the overall
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1:
396:10.1016/S0140-6736(05)66516-6
378:Schulz KF, Grimes DA (2005).
67:-value for the trial is 0.05
48:The Pocock boundary gives a
276:Hall C (5 September 2005).
72:Number of planned analyses
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24:prematurely. The typical
319:10.1001/jama.294.17.2228
357:10.1093/biomet/64.2.191
257:Haybittle–Peto boundary
432:Sequential experiments
442:Design of experiments
390:(9471): 1657–1661.
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437:Clinical research
313:(17): 2228–2230.
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81:-value threshold
75:Interim analysis
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351:(2): 191–9.
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426:Categories
345:Biometrika
263:References
341:Pocock SJ
222:5 (final)
171:4 (final)
130:3 (final)
99:2 (final)
412:26299736
404:15885299
327:16264167
298:(2005).
296:Pocock S
251:See also
59:List of
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225:0.0158
215:0.0158
205:0.0158
195:0.0158
185:0.0158
174:0.0182
164:0.0182
154:0.0182
144:0.0182
133:0.0221
123:0.0221
113:0.0221
102:0.0294
92:0.0294
44:Details
30:placebo
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384:Lancet
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53:-value
408:S2CID
361:JSTOR
303:(PDF)
400:PMID
323:PMID
307:JAMA
16:The
392:doi
388:365
353:doi
315:doi
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