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A student wants to investigate whether people from northern USA are more severely affected by winter depression ("seasonal affective disorder") than people from southern USA, using a questionnaire.

I think this is a one tail test:

H0: u=0

H1: u > 0

Am I correct??

kjetil b halvorsen
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Okidoki
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    Why do you think it is one-tailed instead of two-tailed? – Dave Jun 01 '21 at 22:54
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    Because they are not asking if winter depresion between northern and southern Usa is different from eachother however if winter depresion i northern usa is more severe than southern. We use two tail when we are looking at difference between two variables not if one is either bigger or smaller than the other. What u think? – Okidoki Jun 01 '21 at 23:17
  • I agree with you, unless you came up with your hypothesis after looking at the results and noticing that northerners are affected more than southerners. – Dave Jun 02 '21 at 00:03

1 Answers1

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Yes, as specified you can answer this question with a one-tailed test.

mkt
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  • I have spss for the question above with for instance p value (2tailed) would that mean that i have divide it by 2 since im using one sided test instead of two sided? – Okidoki Jun 02 '21 at 07:40
  • @Okidoki Depends on the direction you are interested in. "depending on the direction of the one-tailed hypothesis, its p-value is either 0.5*(two-tailed p-value) or 1-0.5*(two-tailed p-value) if the test statistic symmetrically distributed about zero. " From https://stats.idre.ucla.edu/other/mult-pkg/faq/general/faq-what-are-the-differences-between-one-tailed-and-two-tailed-tests/ – mkt Jun 02 '21 at 07:50