tag:blogger.com,1999:blog-21831384.post4340229192979962594..comments2019-10-03T14:11:35.530+05:30Comments on BzST | Business Analytics, Statistics, Teaching: The value of p-values: Science magazine asksGalit Shmuelihttp://www.blogger.com/profile/06119270323184007583noreply@blogger.comBlogger12125tag:blogger.com,1999:blog-21831384.post-85204802722579295102009-12-11T01:06:36.720+05:302009-12-11T01:06:36.720+05:30Thanks Shalin -- cool example! Here is a URL that ...Thanks Shalin -- cool example! <a href="http://www.vhpharmsci.com/decisionmaking/Therapeutic_Decision_Making/Fundamentals_files/To%20P%20or%20Not%20to%20P-%20Why%20Use%20a%20P%20Value%20Anyway-MS.pdf" rel="nofollow">Here is a URL</a> that has this article publicly available.Galit Shmuelihttps://www.blogger.com/profile/06119270323184007583noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-85114318148748452672009-12-10T20:01:01.925+05:302009-12-10T20:01:01.925+05:30Besides being misunderstood, I think making a deci...Besides being misunderstood, I think making a decision based on p-values can sometimes magnify the actual advantage of making one choice over the other. There was an interesting article that I had come across - http://www.medscape.com/viewarticle/524206 (To P or Not to P: Why Use a P Value, Anyway?). The author here provides an example in making a choice between 2 bicycle routes from work to homeUnknownhttps://www.blogger.com/profile/11258526964085851720noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-41082262009751741352009-12-09T23:51:01.351+05:302009-12-09T23:51:01.351+05:30Yeah I definitely agree on that point. I think the...Yeah I definitely agree on that point. I think the thing about the p-value is that it's one of those things that everyone is "comfortable with." Kind of like how the "unemployment rate" that is reported is often misunderstood (how it doesn't include people who are not actively looking for jobs and that it excludes people with only part time jobs). To an economist, thisUnknownhttps://www.blogger.com/profile/17470061301232312602noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-70276664355830124112009-12-09T19:07:01.510+05:302009-12-09T19:07:01.510+05:30Fan - I agree that simple is good. It's all ab...Fan - I agree that simple is good. It's all about parsimony. The problem is that p-value is mis-understood. A confidence interval is just as simple and less prone to error.Galit Shmuelihttps://www.blogger.com/profile/06119270323184007583noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-54469957359252465592009-12-09T19:02:54.559+05:302009-12-09T19:02:54.559+05:30I have mixed feelings on the whole thing. While I ...I have mixed feelings on the whole thing. While I do disapprove of over interpreting statistical figures, there are "costs" to consuming more accurate information.<br /><br />When I was in high school doing the student newspaper, we always had to include more or less all the relevant facts in the first two paragraphs because we knew very few people would read beyond that. I used to be Unknownhttps://www.blogger.com/profile/17470061301232312602noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-80681660388535737812009-12-09T02:29:49.747+05:302009-12-09T02:29:49.747+05:30Hi Rob - interesting perspective! When I think of ...Hi Rob - interesting perspective! When I think of a recent blood test that I did, the report was a list of components, each with a confidence interval and a note whether my number was within that interval or not. My doctor explained that just picking the extreme numbers and treating them would be nonsense. Instead, one has to look at the whole picture including the "within-interval" Galit Shmuelihttps://www.blogger.com/profile/06119270323184007583noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-17156597301626183222009-12-09T02:22:46.149+05:302009-12-09T02:22:46.149+05:30Its true, in the west we are very reductionist. W...Its true, in the west we are very reductionist. We like to isolate single variables in complex systems, and hope that leads us to understand the system itself. I think this tendency is what causes us to look for simple numerical thresholds that provide us with a clear yes/no. Fuzziness is hard for the western mind to deal with.Rob Whitenerhttps://www.blogger.com/profile/16203931624356313598noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-78162798140693813372009-12-08T21:55:44.292+05:302009-12-08T21:55:44.292+05:30I agree that culture is one of the driving forces ...I agree that culture is one of the driving forces in the reliance on the p-value. Many introductory courses teach the "simple rule" that anything with a p-value less than .05 is to be considered important. That simple rule then drives results interpretation. While the rule is remembered by many, few remember the associated caveats. I have found that is hard to move away from the Unknownhttps://www.blogger.com/profile/07784256514819036422noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-89159121801157306392009-12-08T20:36:58.676+05:302009-12-08T20:36:58.676+05:30The normal assumption, when adequate, is very powe...The normal assumption, when adequate, is very powerful. When violated, it depends what you are trying to do. If prediction, then perhaps not too bad (but this should be assessed through a holdout set or a similar method). If for inference, then indeed you can be way off. Statisticians will always look at residuals for assessing normality (and perhaps some normality tests with p-values...). In SixGalit Shmuelihttps://www.blogger.com/profile/06119270323184007583noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-84455953632008993822009-12-08T20:08:51.880+05:302009-12-08T20:08:51.880+05:30Relating to the p-value point, another fundamental...Relating to the p-value point, another fundamental flaw is assuming a normal distribution for almost every matter. It has become a tradition to not only use p-values excessively and inappropriately, but also with the wrong distribution assumption, which further exacerbates the flaw of their outputs. Although quality controls systems, such as Six-Sigma are great tools, but with abnormal skewness Khalilhttps://www.blogger.com/profile/00820369784010634472noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-47250084775641900832009-12-08T18:29:29.915+05:302009-12-08T18:29:29.915+05:30Indeed -- this very popular definition is correct,...Indeed -- this very popular definition is correct, although very cryptic. It also means that you have to keep in mind what is the alternative hypothesis, whether it is one- or two-sided, etc. You get so bogged down in these details that it is very likely to forget what it really means and how this relates to practical importance.Galit Shmuelihttps://www.blogger.com/profile/06119270323184007583noreply@blogger.comtag:blogger.com,1999:blog-21831384.post-90174497602377646472009-12-08T09:56:25.923+05:302009-12-08T09:56:25.923+05:30The Albright book uses the dreaded word probabilit...The Albright book uses the dreaded word probability in it's definition of p-value. <br /><br />"The p-value of a sample is the probability of seeing a sample with at least as much evidence in favor of the alternative hypothesis as the sample actually observed. The small the p-value, the more evidence there is in favor of the alternative hypothesis." pg 485JGeraghtyhttps://www.blogger.com/profile/01379781057571394738noreply@blogger.com