CV from CI [Power / Sample Size]

posted by Helmut Homepage – Vienna, Austria, 2018-02-05 12:39 (1880 d 16:24 ago) – Posting: # 18346
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Hi Louis,

❝ 1. Presumably, n1 and n2 are form the previous study, right?

As already explained these are the number of subjects / sequence (TR or RT). If known, fine. The calculated CV will be exact (to the numeric precision of the input). If unknown (rarely given in the literature) use the total number of subjects N and split it in such a way that the study is as balanced as possible. If the study was more unbalanced than assumed you will get a CV which is higher than the true one. Since this is conservative you will be one the safe side basing your sample size estimation on it (see there for an example).

❝ 2. Where 0.91 and 1.15 are coming from? Did you select them just as an example or there is a particular reason?

What do you think the word example in

■ Example: 90% CI [0.91 – 1.15], N 21 (n1 = 11, n2 = 10)

in this presentation means?

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