Brief Conceptual Question

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Brief Conceptual Question

 Dear Colleagues,                          I am a Master's candidate in Psychology, and I'm currently studying for an exam about statistics and research methodology. There was just one conceptual question that I could not seem to find an adequate answer to. The question is as follows: Explain the relationship between sample size and statistical significance testing. Why is the size of an F ratio is bigger with a larger sample size? What does this imply?                      I very much appreciate any feedback anyone can offer! Thank you in advance for your responses. Have a wonderful weekend. Best, Carrie Margulies
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Re: Brief Conceptual Question

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Re: Brief Conceptual Question

 To be a little picky - At 11:26 PM 6/23/2006, Hector Maletta wrote: See phrase in brackets and caps: >1. The larger the sample, the greater the statistical significance of >a statistical result UNEXPLAINED VARIANCE IN THE DATA>. This means that the larger the >sample, the lower the chance that the result is just a fluke or chance >occurrence. >2. If F is above a certain minimum value, you can bet (with a certain >degree of confidence) that the proportion of variance explained by >your model is not zero. Alas, not so; confidence levels tell you something different, and much less satisfying. What Hector is describing is called the *a posteriori* probability that you have a false positive result THIS TIME. The significance level is the *a priori* probability of getting a result this strong, in the absence of any true underlying effect.
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Re: Brief Conceptual Question

 Picky indeed, Richard. In my first point, of course I am referring to the same result, only obtained from two samples of different size. In my second one, the difference is immaterial for the question asked. In both a priori and a posteriori interpretations the idea is the same for the purpose of the question. I tried to keep my answer as simple as possible for the benefit of our colleague asking the question, who may be confused by too many niceties. Hector -----Mensaje original----- De: Richard Ristow [mailto:[hidden email]] Enviado el: Saturday, June 24, 2006 1:48 AM Para: Hector Maletta; [hidden email] Asunto: Re: Brief Conceptual Question To be a little picky - At 11:26 PM 6/23/2006, Hector Maletta wrote: See phrase in brackets and caps: >1. The larger the sample, the greater the statistical significance of >a statistical result UNEXPLAINED VARIANCE IN THE DATA>. This means that the larger the >sample, the lower the chance that the result is just a fluke or chance >occurrence. >2. If F is above a certain minimum value, you can bet (with a certain >degree of confidence) that the proportion of variance explained by >your model is not zero. Alas, not so; confidence levels tell you something different, and much less satisfying. What Hector is describing is called the *a posteriori* probability that you have a false positive result THIS TIME. The significance level is the *a priori* probability of getting a result this strong, in the absence of any true underlying effect.
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