tag:blogger.com,1999:blog-6894866515532737257.comments2014-07-25T13:46:08.499-07:00Probably Overthinking ItAllen Downeyhttps://plus.google.com/111942648516576371054noreply@blogger.comBlogger377125tag:blogger.com,1999:blog-6894866515532737257.post-34903015756005710772014-07-25T13:46:08.499-07:002014-07-25T13:46:08.499-07:00Great, thanks Allen. I see your odds ratio but wh...Great, thanks Allen. I see your odds ratio but what was your overall pseudo r-squared? Larry Featherstonhttp://www.blogger.com/profile/16772361721940706273noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-90191702517436045032014-07-25T10:56:30.285-07:002014-07-25T10:56:30.285-07:00Hi Larry,
All of my code and the data are in this...Hi Larry,<br /><br />All of my code and the data are in this repository:<br /><br />https://github.com/AllenDowney/internet-religion<br /><br />You should be able to check it out and replicate my results easily, especially if you have a Python environment set up.<br /><br />The paper, with details about the methodology and the variables I used, is here:<br /><br />http://arxiv.org/abs/1403.5534<br /><br />Let me know if you find anything interesting!<br /><br />AllenAllen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-62477961359659649502014-07-25T10:49:12.514-07:002014-07-25T10:49:12.514-07:00Hi Allen,
I am intrigued by your research on int...Hi Allen, <br /><br />I am intrigued by your research on internet usage and religion and have a few questions. In the 2012 General Social Survey dataset, I am familiar with several variables related to internet usage. Some of these variables are binomial and others are interval-scaled such as the WWWHR variable. <br /><br />To help me understand your research, can you provide the model specification you used for your analysis? I would like to replicate the results and would like to see your beta weights and pseudo R-square values which you are basing your interpretation? You also indicated that you utilized logistic regression to perform your analysis. Could you provide a little more detail about your statistical methodology? Did you perform a multinomial logistics regression or ordinal regression? <br /><br />Thanks so much,Larry Featherstonhttp://www.blogger.com/profile/16772361721940706273noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-30767234136153558712014-07-23T08:10:28.624-07:002014-07-23T08:10:28.624-07:00Nice!Nice!Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-38985412746039363392014-07-23T07:15:56.542-07:002014-07-23T07:15:56.542-07:00Well, not 'where' but 'how' :-) I ...Well, not 'where' but 'how' :-) I used Mathematica to make the integration and R to find the mode. The details are at the end of the webpage I made.<br /><br />Cheers,João Netohttp://www.blogger.com/profile/05560718055133816500noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-82580042191608181412014-07-23T07:08:09.613-07:002014-07-23T07:08:09.613-07:00Huh. Well, let me know if you figure it out.
Whe...Huh. Well, let me know if you figure it out.<br /><br />Where did you find the analytic solution?Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-76711349270150731902014-07-19T10:55:22.346-07:002014-07-19T10:55:22.346-07:00I found the analytic solution for p(n|data) and th...I found the analytic solution for p(n|data) and the mode is at 72.18 which confirms your result. My result for the mode with the uniform prior is at 75.9. I really don't know what is causing this difference but I suppose it is from my BUGS model. Oh well...João Netohttp://www.blogger.com/profile/05560718055133816500noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-79206650998399083122014-07-18T11:52:13.861-07:002014-07-18T11:52:13.861-07:00Yes, good point. Thanks!Yes, good point. Thanks!Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-22451905110809727862014-07-18T11:27:50.159-07:002014-07-18T11:27:50.159-07:00I think it should be noted that the assumption tha...I think it should be noted that the assumption that all error probabilities are the same makes a big difference. Suppose I have a program with 100 bugs, 5 of which are easy to find, and two testers who are bad at finding bugs. Tester 1 finds 10 bugs (including all 5 easy ones), tester 2 finds 10 bugs (including all 5 easy ones), and the intersection is the 5 easy ones. The Lincoln index would estimate 20 bugs and your method would find something similar (I'm assuming, I didn't implement the code). In general, the more the probabilities differ from error to error, the more these methods will underestimate the total number of errors. They do work quite well, though, when error probabilities are uniform. Bryanhttp://www.blogger.com/profile/15975987326012523061noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-15912748967488529342014-07-17T15:18:00.184-07:002014-07-17T15:18:00.184-07:00Whenever I see a single author use "we" ...Whenever I see a single author use "we" for self-reference, I always wonder whether to attribute this to pregnancy or tapeworms. The New York Times Magazine had an article on this subject: <br />http://www.nytimes.com/2010/10/03/magazine/03FOB-onlanguage-t.html?_r=0Left In Sighthttp://www.blogger.com/profile/06491379217627155467noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-35114467506693942042014-07-15T08:55:18.324-07:002014-07-15T08:55:18.324-07:00Much better than the Cooke post. Cooke's post...Much better than the Cooke post. Cooke's post has a flaw - if you send an app to a million beta testers, and 5000 users find a few bugs, your bug count projection spirals high very quickly (since the numerator ultimately becomes an exponential function).<br /><br />I intend to give this a whirl and see what numbers I get.534a2a4a-0c38-11e4-ac97-cfc4eb6ea870https://openid.aol.com/opaque/534a2a4a-0c38-11e4-ac97-cfc4eb6ea870noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-37603483965944803822014-07-11T07:37:03.607-07:002014-07-11T07:37:03.607-07:00Huh. I'm baffled for now. Let me know if you...Huh. I'm baffled for now. Let me know if you learn more.Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-92080627314854601042014-07-11T06:51:40.269-07:002014-07-11T06:51:40.269-07:00With an uniform prior, the mean for 'n' is...With an uniform prior, the mean for 'n' is 108.9 and the MLE estimate is 78. I think this makes sense, since the uniform gives move probability mass to the upper values, relative to the exponential. However, this result produces even a bigger difference between our results (?)<br /><br />The simulation run took 2 seconds.<br /><br />I assume that it is a problem with my model, but in my defense the simulation I do at the end for the expected value of 'c' is very near 3 :-) With the exponential the simulated result was 2.98. With the uniform the result was 2.95.João Netohttp://www.blogger.com/profile/05560718055133816500noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-2108579856498488812014-07-11T06:30:08.563-07:002014-07-11T06:30:08.563-07:00That's excellent -- thanks!
My results are ba...That's excellent -- thanks!<br /><br />My results are based on a uniform prior for n, which was an arbitrary choice, not motivated by any background knowledge. That might explain the difference between your results and mine, but I agree with you that it seems like a big difference.<br /><br />Can you run yours again with a uniform prior on [32, 350]?<br /><br />Also, how long does your model take to run?Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-65199642275224221332014-07-11T05:48:08.128-07:002014-07-11T05:48:08.128-07:00Thanks for this interesting post.
I have implemen...Thanks for this interesting post.<br /><br />I have implemented your model in BUGS and the mean results were n=106 (like your solution), p1=0.22, p2=0.17. However, the MLE estimate that I got is 77, which is a bit far from your 72 estimate. The prior for n must have been different (I used a truncated exponential with very low lambda) but even so it seems a big difference.<br /><br />The code and results are here: http://www.di.fc.ul.pt/~jpn/r/bugs/lincoln.html<br /><br />Cheers,João Netohttp://www.blogger.com/profile/05560718055133816500noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-88200489576209646852014-06-28T10:42:06.275-07:002014-06-28T10:42:06.275-07:00I Interesting post. I have been wondering about th...I Interesting post. I have been wondering about this issue,so thanks for posting.<br />To get new information visit here <br /><a href="http://pluslaw.com.au/services/payless_conveyancing.shtml" rel="nofollow">conveyancing nsw</a><br /><a href="http://pluslaw.com.au/services/payless_conveyancing.shtml" rel="nofollow">conveyancing newcastle</a>conveyancin664http://www.blogger.com/profile/00819221129172428404noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-25485960951800677422014-06-19T02:02:14.035-07:002014-06-19T02:02:14.035-07:00This comment has been removed by the author.Ramiz Razahttp://www.blogger.com/profile/09941047122119668254noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-29219235425542171722014-06-04T13:13:38.799-07:002014-06-04T13:13:38.799-07:00Dr. Downey -
Thanks so much for your reply. I wi...Dr. Downey -<br /><br />Thanks so much for your reply. I will definitely be interested in the results of your experiments and further thought on the matter. In the meantime, I will make my way through ThinkBayes. This approach to solving problems is relevant to my work right now, as we are attempting to make some judgments with varying amounts of data, so I'm very happy to have your book as a guide.<br /><br />Take care,<br /><br />SteveSThttp://www.blogger.com/profile/06615807234500868464noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-54378153038676955942014-06-04T06:01:14.824-07:002014-06-04T06:01:14.824-07:00Hi, Steve. This is a great question, and one I am...Hi, Steve. This is a great question, and one I am thinking about myself. When I started Think Bayes I imagined that I would start with simple methods and switch to pyMC when needed. But I found that for the case studies that I wanted to do, the simple methods were sufficient, so I never made the switch.<br /><br />When I have a chance to get back to it, I want to reimplement some of my solutions using pyMC and try to answer your question: when to prefer one or the other, and how to make a smooth transition from one to the other.<br /><br />One way to think about the difference is that pyMC generates samples from the posterior distribution, so you let it run as long as necessary to generate a posterior with sufficient precision. The method in Think Bayes is basically enumeration of the posterior or a discrete approximation to it. So it takes a fixed amount of time and yields high precision, but the run time grows exponentially with the number of dimensions / number of parameters you are trying to estimate. And that's not practical for more than 3-4 parameters.<br /><br />Thanks for asking!Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-25716699635394134662014-06-04T05:14:39.895-07:002014-06-04T05:14:39.895-07:00Hi, Dr. Downey -
I am continuing to watch your pr...Hi, Dr. Downey -<br /><br />I am continuing to watch your presentations online and also digging into ThinkBayes. Thank you for your work in this area, and your commitment to teaching. <br /><br />I'm new to the whole area of probabilistic programming, and ran into your book and lectures after I found pyMC. Honestly, I had a little difficulty following some of the reasoning in their examples, at least on the first pass through initial chapters, but your book is helping to clarify the concepts.<br /><br />The question emerging in my mind, now that I'm starting into your book and code is, when is it appropriate to use your approach/code vs. pyMC? Should I understand your book as more conceptual, and then move on to use pyMC in practice? Would pyMC be as performant (or more?) as your code for the problems you cover, or does it involve simulation and therefore require more CPU cycles? Being new, again, and facing these options, I feel like I need a little more in the way of the lay of the land. <br /><br />Thank you for your time. Regards,<br /><br />Steve SThttp://www.blogger.com/profile/06615807234500868464noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-77975566003597897232014-06-03T11:31:30.263-07:002014-06-03T11:31:30.263-07:00Thanks! We're still kicking this decision aro...Thanks! We're still kicking this decision around, so thank you for your thoughts.<br />Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-74007116642783542822014-06-03T11:15:46.709-07:002014-06-03T11:15:46.709-07:00Hey Allen,
Just a quick note because it caught my...Hey Allen,<br /><br />Just a quick note because it caught my eye that you are considering moving ModSim over to Python. While I much prefer Python over MATLAB and did not particularly enjoy the MATLAB portion of ModSim, looking back I think it was a valuable experience and MATLAB is a good tool to have under your belt throughout many of Olin's courses. I would advise against making that change.<br /><br />I also hope that you continue to keep the cat on the cover of the physical copies. :)<br /><br />Best,<br />AriArihttp://www.blogger.com/profile/17929105166366737318noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-32729520169278376572014-05-28T10:03:55.804-07:002014-05-28T10:03:55.804-07:00That's funny. Thanks!That's funny. Thanks!Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-30015951511152233472014-05-28T09:42:04.241-07:002014-05-28T09:42:04.241-07:00I realize this is an older post, but it is great s...I realize this is an older post, but it is great stuff; I was watching your video on YouTube that covers this material and stopped to work it out myself. On the m&m problem, there are actually two issues: one which you've outlined above, but the second could be stated as, "What are the chances that the dispenser of m&m's is not a good friend, given the early date of those bags of candy?!" http://www.eatbydate.com/other/sweets/mms/<br /><br />Thanks again, your work is much appreciated.<br /><br />SteveSThttp://www.blogger.com/profile/06615807234500868464noreply@blogger.comtag:blogger.com,1999:blog-6894866515532737257.post-46318838860126082102014-05-19T08:47:34.755-07:002014-05-19T08:47:34.755-07:00Looks good. Thanks for the link!Looks good. Thanks for the link!Allen Downeyhttp://www.blogger.com/profile/01633071333405221858noreply@blogger.com