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Dr Andrew Leary ★ Ireland, 2010-05-27 18:03 (5872 d 07:02 ago) Posting: # 5386 Views: 5,753 |
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Greetings Helmut et al! Please excuse the trivial question. I blame medical training, which is short both on mathematics and logic. If I were to run a four period replicate design study in n=24, this has the statistical power of a standard two-way design in n=48 (along with the added advantage of being able to apply wider limits using SABE). If I instead choose to run a three period replicate study with equivalent power, my understanding this should include n=36. However, in this case the T/R comparison involves 36 sets of data, while the 4-period design involves 48 T/R comparisons. Surely that gives the 4-period design an advantage? Where has my logic gone wrong? Kind regards Andrew |
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Helmut ★★★   Vienna, Austria, 2010-05-27 18:28 (5872 d 06:38 ago) @ Dr Andrew Leary Posting: # 5387 Views: 4,856 |
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Dear Andrew! ❝ [...] trivial question. I blame medical training, which is short both on ❝ mathematics and logic. Well, you already made an important step! To quote Stephen Senn: Statistics - A subject which most statisticians find difficult ❝ If I were to run a four period replicate design study in n=24, this has the ❝ statistical power of a standard two-way design in n=48 (along with the added ❝ advantage of being able to apply wider limits using SABE). If I instead ❝ choose to run a three period replicate study with equivalent power, my ❝ understanding this should include n=36. So far, so good. ❝ However, in this case the T/R comparison involves 36 sets of data, while ❝ the 4-period design involves 48 T/R comparisons. Ha, tricky! In the 2×2 you have 48 T/R comparisons. But in a replicate design means of the repeated administrations are compared - in the 3-way 36 and in the 4-way 24. This averaging and the modified degrees of freedom of the variances involved lead to the same power. — Dif-tor heh smusma 🖖🏼 Довге життя Україна! ![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png) Helmut Schütz ![[image]](https://static.bebac.at/img/CC by.png) The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
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Dr Andrew Leary ★ Ireland, 2010-05-27 18:46 (5872 d 06:20 ago) @ Helmut Posting: # 5388 Views: 4,717 |
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Many thanks, Helmut Statistics - A subject which most statisticians find difficult but in which nearly all physicians are expert. Excellent! One to remember for anytime you're lecturing medics! Kind regards Andrew |
Ing. Helmut Schütz