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I had an exam with a question (multiple choice) that had this question:

If I perform a test with a significance level of alpha = 0.05 and reject H0 for a one-sided test, it means that:

A) I reject H0 for a bilateral test with alpha = 0,1

B) I reject H0 for a bilateral test with alpha = 0.025

C) I can not conclude anything for the bilateral test

I answered the C because it seemed to me already to have heard that we could say nothing on a bilateral test by having performed a unilateral test but I'm afraid of making a mistake haha!

So if someone can tell me if this answer is the right and if yes / no, why?

kjetil b halvorsen
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M. Warzowski
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    Please see our [help/on-topic] on homework-style questions (this includes current and past exam questions, textbook exercises and so on), and read the material linked there. Your indicated reasoning doesn't contain any reasoning ("I seem to have heard" is next to useless as reasoning - what if what you heard was wrong?). My advice would always be to draw a picture. In this case if you draw both rejection regions for option A and for option B you should immediately be able to see which of the three answers is correct. – Glen_b Aug 20 '18 at 00:54
  • Ok I think I understood. If I draw the reject region for a 5% unilateral test I will have 5% of the area (right or left) where I will reject H0. If I do a bilateral test with 10% I will have 5% left and right for the rejection region so solution A is the right one? – M. Warzowski Aug 20 '18 at 01:29
  • It seems like you have the sense of it now. You might consider posting an answer (with such a drawing if you can manage it) – Glen_b Aug 20 '18 at 02:27
  • But I have an other question. Here, it's ok for the 'A' because we consider bell shaped distribution but it could be an asymetric distribution and so the right answer would be 'C' no? – M. Warzowski Aug 20 '18 at 18:41
  • It depends -- how much area will you place in each tail when you do your asymmetric two tailed test? Many people are simply taught to put half the area in each tail no matter what and they should conclude that the examiner will want A. People that have been taught other possibilities might indeed consider C as a better answer. (My expectation is that the examiner will expect A here, but I can't tell your circumstances.) – Glen_b Aug 20 '18 at 23:44

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