Theta?! [Software]

posted by Helmut Homepage – Vienna, Austria, 2009-10-01 19:30 (5292 d 11:20 ago) – Posting: # 4287
Views: 24,874

Dear Yuvraj!

❝ I have read the sample size calculation formula for parallel design.


Which one? Can you come up with a reference?

❝ I have one query regarding parameter Theta


Theta (θ) commonly refers to the regulatory ‘goalposts’ or acceptance limits. For an acceptable difference (Δ) of 0.2 (or 20%) in the multiplicative model we get:

θ1 = 1–Δ (80%), and
θ2 = 1/(1+Δ) = 1/θ1 (125%).
In the logarithmic domain the acceptance range is symmetric around zero, since
ln1) = –0.2231 and
ln2) = +0.2231.

In the linear model (untransformed data):

θ1 = 1 – Δ (80%), and
θ2 = 1 + Δ (120%).


Theta=(muT-muR)/muR

❝ is it a T/R ratio ?


No, this is the difference normalized to the reference. :-D
T =  95, R = 100 ⇒ –0.05 (ratio 0.95)
T = 190, R = 200 ⇒ –0.05 (ratio 0.95)

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