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[ODP] Immigrant GPA in Danish primary school is predictable from country-level variab

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Quote:Of course not. I saw it many times my variables normally distributed when looking at histogram and P-P plot, and yet S-W says otherwise. Like i said: it's p-value. Your argument is similar as saying that if p is significant, it can only be so if the effect size is large. Yet that is not true, and a lot of examples show that the effect size can be close to zero but p is significant. One example you have is from Pekkala Kerr et al. (2013) "School tracking and development of cognitive skills". They say that schooling reform shows no transfer effect, just because some tests are significantly improved, and others not. But when you calculate effect sizes, which they don't, the d gaps are between 0.00 and 0.03 (or 0.04). In my opinion, it's not different than to say the effect size is zero for each test.

The p value will only go down if the data are non-normal. With large N's, even a slight deviation from normality will cause a low p value. However, merely using a large N is not sufficient, as I just showed with code above (N=5000).

My argument is not one of the fallacies which is you discuss, where authors reason from "significant p value" to "real-world significance" or from "non significant p-value" to "no effect".

Quote:It's dangerous to use significance tests. I always said it, and I will always repeat it.

And even if you trust W value, I don't trust cut off values. What is the .99 really means, given the operation to get W value, which is given here?

So, what does that mean when you have 0.95 or 0.96 instead of 0.99 ? How can you judge that ? If you think eye-balling is not nice, I will say cut-off values are not better.

W = 1 perfect normality. Any value below it indicates non-normality. We can simulate datasets, so one can get a feel for the different values of W and how the data looks like. I did a little write-up here: http://emilkirkegaard.dk/en/?p=4452

As you can see from my simulations, W values do not change much as long as the distribution is reasonably normal. It was hard to get it below .95. Of course, when examining small datasets, such as the GPA one (N=19), sampling error can result in low W values even tho the population GPA distribution is normal (or normalish).

In the case of GPA here, however, it is not very normal. I tried log-transforming it, but it is slightly less normal after that (Ws .9251 before, .9124 after). What do you want me to do with it?
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Messages In This Thread
[ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-02, 00:49:54
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Nov-02, 03:13:04
Normality - by Emil - 2014-Nov-02, 05:37:41
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Nov-02, 19:21:44
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-02, 19:32:02
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Nov-02, 20:15:44
Shapiro test - by Emil - 2014-Nov-02, 22:39:48
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Nov-03, 19:29:29
Spearman - by Emil - 2014-Nov-03, 04:17:20
Nonnormal - by Emil - 2014-Nov-03, 22:59:31
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Nov-06, 01:32:32
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-06, 01:48:01
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-06, 02:46:26
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Nov-06, 02:59:02
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-06, 03:57:07
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Nov-06, 20:48:41
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-07, 02:31:06
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Nov-07, 20:24:16
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-09, 04:19:00
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-26, 19:38:54
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2014-Dec-30, 00:35:58
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-Jan-12, 22:12:58
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Jan-14, 14:28:28
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-Jan-25, 01:51:01
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Nov-27, 23:31:16
I have updated the paper to draft #4 - by Emil - 2014-Nov-29, 08:20:32
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2014-Dec-05, 01:19:52
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Dec-05, 10:54:41
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2014-Dec-27, 05:57:01
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Meng Hu - 2015-Jan-05, 19:33:18
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Peter Frost - 2014-Dec-30, 23:31:30
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Jan-14, 15:00:45
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Jan-13, 00:13:23
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Jan-25, 02:43:12
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Feb-02, 16:58:19
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-Feb-02, 19:21:15
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Feb-02, 20:34:14
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-Feb-02, 21:12:06
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Feb-03, 03:48:24
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Feb-05, 17:14:10
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-Feb-08, 03:52:29
Reply to John's #41 - by Emil - 2015-Feb-09, 04:15:15
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-Feb-11, 04:26:03
Draft #6 - by Emil - 2015-Feb-17, 05:04:22
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-Mar-12, 22:05:36
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Mar-13, 00:50:20
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Peter Frost - 2015-May-24, 18:13:12
Reply to Peter #47 - by Emil - 2015-May-26, 07:56:34
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Peter Frost - 2015-May-26, 18:42:03
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-May-26, 23:00:21
RE: [ODP] Immigrant GPA in Danish primary school - by Meng Hu - 2015-May-28, 08:32:30
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-May-28, 23:16:31
Reply to MH #51 - by Emil - 2015-May-28, 10:09:59
RE: [ODP] Immigrant GPA in Danish primary school - by Meng Hu - 2015-May-28, 17:34:38
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-May-28, 23:25:35
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Chuck - 2015-May-30, 19:52:15
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Jun-04, 14:36:24
RE: [ODP] Immigrant GPA in Danish primary school is predictable from country-level variab - by Emil - 2015-Jun-04, 18:15:24
 
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