Re: Proportionate vs. disproportionate
In article <[EMAIL PROTECTED]>, EugeneGall <[EMAIL PROTECTED]> wrote: > I too think that the odds ratio is the appropriate way to present > the data, but after looking at these results, I can appreciate why > the Gallup organization didn't do so. > > The data on racial favorability ratings which Gallup called > 'proportionate' not 'disproportionate': > > GWBush favorability pre- and post-9/11 > Pre-disasterPost-disasterOddsRatio > White (odds) 60% (1.5)90% (9)6 > Black (odds) 33% (0.49) 68% (2.1) 4.3 > > GHBush favorability pre- and post-Gulf War > Pre-disasterPost-disasterOddsRatio > White (odds) 64% (1.8) 90% (9) 5.1 > Black (odds)33% (0.49)70% (2.3) 4.7 > > Unless I'm missing something, a logistic regression analysis with > disaster and race coded as dummy variables with an interaction term > (disaster x race) would have a sign for the interaction coefficient > indicating that the odds of white favorability for Bush after a > disaster increased more than the increase in black favorability for > Bush after a disaster. This is NOT what I'd expected after looking > at the raw percentages, which to me indicated a disproproportionate > increase in black favorability for the Bushes after disasters. I think you're all reading too much into this data. A simple examination of the the 9/11 and Gulf War numbers shows that there is virtually no difference in all four of the numbers (60% vs. 64%, 68% vs. 70%, others identical). Since people's opinions are presumably influenced by other issues, not to mention the weather at the time the poll is conducted, drawing any conclusion to the effect that the two disasters had different political effects would be ridiculous. As for the data on just one disaster (say 9/11), it's silly to summarize it, or to describe the changes as "proportionate" or not. There are just four numbers. Anyone can look at them and draw their own conclusions. Nothing is gained by attempting to interpret them in terms of odds ratios. There is no reason to think that a logistic regression model is going to provide insight into the extremely complex interactions of factors (most invisible in this data, of course) that determine people's political opinions. To mention just one possibility, there may well be groups of people who would never say they approve of Bush, or never say they don't approve, because of ideological committments having nothing to do with 9/11, which they are very unlikely to abandon. Any logistic regression style model would then be more appropriately applied only to the people with more malleable opinions. The regression coefficients obtained from this model (if one could fit it, which one can't, of course) could well be quite different from those obtained on the whole data set. Radford Neal Radford M. Neal [EMAIL PROTECTED] Dept. of Statistics and Dept. of Computer Science [EMAIL PROTECTED] University of Toronto http://www.cs.utoronto.ca/~radford = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
Rich Ulrich wrote: >I am not positive, but >I think I would have objected to "equal % change" >as =proportionate= by the time I finished algebra in high school. > >I know I have objected to similar confusion, on principled >grounds, since I learned about Odds Ratios. > >I suspect that the original sample was small enough that >the apparent difference in ORs was not impressive. >-- > I too think that the odds ratio is the appropriate way to present the data, but after looking at these results, I can appreciate why the Gallup organization didn't do so. The data on racial favorability ratings which Gallup called 'proportionate' not 'disproportionate': GWBush favorability pre- and post-9/11 Pre-disasterPost-disasterOddsRatio White (odds) 60% (1.5) 90% (9) 6 Black (odds) 33% (0.49) 68% (2.1) 4.3 GHBush favorability pre- and post-Gulf War Pre-disasterPost-disasterOddsRatio White (odds)64% (1.8) 90% (9)5.1 Black (odds)33% (0.49)70% (2.3) 4.7 Unless I'm missing something, a logistic regression analysis with disaster and race coded as dummy variables with an interaction term (disaster x race) would have a sign for the interaction coefficient indicating that the odds of white favorability for Bush after a disaster increased more than the increase in black favorability for Bush after a disaster. This is NOT what I'd expected after looking at the raw percentages, which to me indicated a disproproportionate increase in black favorability for the Bushes after disasters. Gene Gallagher UMASS/Boston = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
Perhaps it's just a matter of getting a meaningful denominator. Certainly the 100% of each group which the Gallop presentation uses seems to do violence to the concept of proportional. As Elliot Cramer writes it also doesn't make much sense to use the percent approval before 9/11. But isn't it meaningful to use the percent disapproval before 9/11? Then if white approval went from 60% to 90% his disapproval dropped 75% and if black approval went from, say 40% to 70% his disapproval among blacks was only cut in half. 75% compared to 50%. Using these numbes Black disapproval would have to shrink to about 15% from 60% to make a change "proportional" to that of whites (10% from 40%). Elliot Cramer wrote: > On Fri, 11 Jan 2002, Dennis Roberts wrote: > > > > > finally ... i think we are making a mountain out of a molehill in this ... > > to me ... the most important "fact" from the video was that (regardless of > > change and how you define it) ... whites approved of the president to a FAR > > greater extent than blacks ... and, the second most important "fact" was > > that AFTER the event ... the approval ratings for BOTH groups went un > > dramatically > > > > I agree with this; I just don't think that there is any meaningful way of > comparing Black and white increases, given that they start from very > different bases > > = > Instructions for joining and leaving this list, remarks about the > problem of INAPPROPRIATE MESSAGES, and archives are available at > http://jse.stat.ncsu.edu/ > = = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
one traditional way of comparing changes in percentages to to transform to z-scores and then subtracting. I think this is what signal-detection people call D-prime. Elliot Cramer wrote: > On Fri, 11 Jan 2002, Dennis Roberts wrote: > > > > > finally ... i think we are making a mountain out of a molehill in this ... > > to me ... the most important "fact" from the video was that (regardless of > > change and how you define it) ... whites approved of the president to a FAR > > greater extent than blacks ... and, the second most important "fact" was > > that AFTER the event ... the approval ratings for BOTH groups went un > > dramatically > > > > I agree with this; I just don't think that there is any meaningful way of > comparing Black and white increases, given that they start from very > different bases > > = > Instructions for joining and leaving this list, remarks about the > problem of INAPPROPRIATE MESSAGES, and archives are available at > http://jse.stat.ncsu.edu/ > = = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
On 11 Jan 2002 07:46:20 -0800, [EMAIL PROTECTED] (Dennis Roberts) wrote: > definition: proportionate = equal % change > > IF we agree on this ... and maybe we don't ... then, since the % change is > always UN =, then all changes are DISproportionate [ ... ] Are you sure you *advocate* that? I am not positive, but I think I would have objected to "equal % change" as =proportionate= by the time I finished algebra in high school. I know I have objected to similar confusion, on principled grounds, since I learned about Odds Ratios. I suspect that the original sample was small enough that the apparent difference in ORs was not impressive. -- RIch Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
On Fri, 11 Jan 2002, Dennis Roberts wrote: > > finally ... i think we are making a mountain out of a molehill in this ... > to me ... the most important "fact" from the video was that (regardless of > change and how you define it) ... whites approved of the president to a FAR > greater extent than blacks ... and, the second most important "fact" was > that AFTER the event ... the approval ratings for BOTH groups went un > dramatically > I agree with this; I just don't think that there is any meaningful way of comparing Black and white increases, given that they start from very different bases = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
1. well, one can consider proportionate ... equal change VALUES ... and i think that is one legitimate way to view it ... which is how the video guy was talking about it ... 2. one could consider proportionate ... equal change from the BASE ... and i think that is legitimate too ... this is clearly NOT how the video guy was referring to it to sure, if one group goes from 60 to 90 ... this is a change of 30 % points ... and, if another group goes from 30 to 60 ... this is a change of 30% points ... i think it is fair to say that the amount of change % points is the same ... thus proportional now, another way we can view the data is to say that in the first group ... since the base is 60 ... the change of 30 is a 50% change in % points ... compared to the base ... whereas in the second group ... the change from 30 to 60 represents a 100% change from the base ... now, if the base N is the same ... say 600 people ... 30% of 600 = 180 people ... no matter if a group change from 60 to 90 OR 30 to 60 ... thus, if the BASE n is the same ... then both value of % change AND volume of n ... mean the same thing if one group's n = 600 and another group's n = 100 ... these are not the same but in any case ... and the way we usually look at these poll %ages ... is in terms of the absolute value of the % values ... so, in THAT context and the way the public usually views these things ... scenario #1 above is how the video person presented the data ... and in that context i think his presentation did NOT try nor did "snow" the video viewers i don't think there is any natural law that says that proportionate or disproportionate has to be interpreted in terms of scenario #2 above ... finally ... i think we are making a mountain out of a molehill in this ... to me ... the most important "fact" from the video was that (regardless of change and how you define it) ... whites approved of the president to a FAR greater extent than blacks ... and, the second most important "fact" was that AFTER the event ... the approval ratings for BOTH groups went un dramatically if the video guy had made the distinctions in scenarios 1 and 2 above ... and had then interpreted the data under both cases ... i think this would have helped NONE in conveying to the public the information that i (IMHO) think was most important ... we seem to be trying to find something that the fellow was hiding FROM the public when, i don't really think he was trying (nor gallup) to hide anything ... he was presenting some data results ... giving one interpretation of the results ... and, if WE want to interpret them differently ... we can is that not true for any set of results? At 10:58 AM 1/11/02 -0500, you wrote: >On Fri, 11 Jan 2002, Dennis Roberts wrote: > > > if the polls used similar ns in the samples ... i disagree > > > > now, if the white sample was say 600 and the black sample was 100 ... i > > MIGHT be more likely to agree with the comment below > >consider white goes 10% to 15% up 50%, 5%pts > black goes 66.7% to 100% up 50%, 33.3%pts > >These are proportionate but hardly equivalent > >white goes 0 to 50% up infinite %, 50%pts >black goes 50% to 100% up 100%50pts >same %pts but black is more striking >I can't see any kind of equivalence in either case _ dennis roberts, educational psychology, penn state university 208 cedar, AC 8148632401, mailto:[EMAIL PROTECTED] http://roberts.ed.psu.edu/users/droberts/drober~1.htm = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
On Fri, 11 Jan 2002, Dennis Roberts wrote: > if the polls used similar ns in the samples ... i disagree > > now, if the white sample was say 600 and the black sample was 100 ... i > MIGHT be more likely to agree with the comment below consider white goes 10% to 15% up 50%, 5%pts black goes 66.7% to 100% up 50%, 33.3%pts These are proportionate but hardly equivalent white goes 0 to 50% up infinite %, 50%pts black goes 50% to 100% up 100%50pts same %pts but black is more striking I can't see any kind of equivalence in either case = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
if the polls used similar ns in the samples ... i disagree now, if the white sample was say 600 and the black sample was 100 ... i MIGHT be more likely to agree with the comment below At 06:12 PM 1/10/02 -0500, Elliot Cramer wrote: >EugeneGall <[EMAIL PROTECTED]> wrote: >: The Gallup organization posted a video to explain why the the increase in >: black's job approval for Bush is 'proportionate' to the increase among >whites. > >It makes no sense to talk of "proportionate" increases in percentages > >Suppose you start at zero or 99% ... > > > >= >Instructions for joining and leaving this list, remarks about the >problem of INAPPROPRIATE MESSAGES, and archives are available at > http://jse.stat.ncsu.edu/ >= _ dennis roberts, educational psychology, penn state university 208 cedar, AC 8148632401, mailto:[EMAIL PROTECTED] http://roberts.ed.psu.edu/users/droberts/drober~1.htm = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
definition: proportionate = equal % change IF we agree on this ... and maybe we don't ... then, since the % change is always UN =, then all changes are DISproportionate but, given margins of error and the like ... and, just the practical interpretation of the data ... i would say that we could have a pragmatic agreement that if the changes were within P %, then we might "call" the changes = the fact is, if the data are accurate, for both whites and blacks, the after ratings jumped dramatically .. compared to the before ratings ... now we are just quibbling over whether those dramatic jumps should be called = or not thus, the issue in the video and the information that was presented is ... are the changes SO large as to make even tolerant people say that they are different in the case of george w and, the white and black change from pre to post ... i am MORE than willing to concede that they look about the same for the elder bush ... in term of gulf war pre and post ... the changes between approval ratings between whites and blacks i would be less willing to argue that way but, unless we have STANDARD ERRORS OF DIFFERENCES IN PROPORTIONS FOR CORRELATED SAMPLES .. to make the comparisons with, i think it is just an exercise in "whatever you think" about the data i still don't think the person in the video made any egregious misstatements of how the data looked, and in addition ... if you view the data watching the video, which is very clear you could make up your own mind anyway perhaps you could elaborate on why you think he should have been saying DISproportionate all the time ... at what threshold "change" value would have to be evidenced in the data for you to think he should have been speaking in opposite terms? At 09:59 PM 1/10/02 +, EugeneGall wrote: >His definition of proportionate would mean that if a group's approval of Bush >went from 1% to 31%, that too would be proportionate. The relative odds would >be one way of expressing the changes in proportions, but the absolute >difference (60% to 90% is roughly propotionate to an increase from 33% to 68%) >seems quite wrong. > > >= >Instructions for joining and leaving this list, remarks about the >problem of INAPPROPRIATE MESSAGES, and archives are available at > http://jse.stat.ncsu.edu/ >= _ dennis roberts, educational psychology, penn state university 208 cedar, AC 8148632401, mailto:[EMAIL PROTECTED] http://roberts.ed.psu.edu/users/droberts/drober~1.htm = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
Eugene Gall wrote: > His definition of proportionate would mean that if a group's approval of > Bush went from 1% to 31%, that too would be proportionate. The relative > odds would be one way of expressing the changes in proportions, but the > absolute difference (60% to 90% is roughly propotionate to an increase > from 33% to 68%) seems quite wrong. Using relative odds as a definition of changes in proportions would mean that your example of a 30%-units increase from 1% to 31% would, for example, be poroportionate to a 73%-units change from 10% to 83%. Both would have the same odds ratio = 44. Equal differences in percentages means that the same proportion of the population changed their minds. The meaning was probably "proportionate" = "of the same order of magnitude". Rolf Dalin = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
EugeneGall <[EMAIL PROTECTED]> wrote: : The Gallup organization posted a video to explain why the the increase in : black's job approval for Bush is 'proportionate' to the increase among whites. It makes no sense to talk of "proportionate" increases in percentages Suppose you start at zero or 99% ... = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
His definition of proportionate would mean that if a group's approval of Bush went from 1% to 31%, that too would be proportionate. The relative odds would be one way of expressing the changes in proportions, but the absolute difference (60% to 90% is roughly propotionate to an increase from 33% to 68%) seems quite wrong. = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Re: Proportionate vs. disproportionate
there are two sets of data ... one for georgeDUBU ... and the elder george bush here is what i glean from the charts for george w ... the EVENT was sept 11 ... for the elder george bush ... the EVENT was the gulf war ... and both were before and after ratings 1. whites approval rating for BOTH ... was much higher than blacks 2. both whites and blacks jumped rather dramatically (in the 30 percent range) on AFTER compared to BEFORE 3. to me, proportionate would be "both increasing" the same approximate % ... disproportionate would imply large differentials in % changes ... in neither case were the % jumps the same ... for each bush ... before and after ... comparing whites and blacks (assuming the data reported in the video is correct) ... so TECHNICALLY ... it is disproportionate ... but ... what about "approximately" ??? i think it is a matter of practical differences and semantics ... not really statistically significant differences ... given the ns ... it is possible that the difference in THE differences MIGHT have been significant ... here are the values george w ... WHITES pre post change 60 9030 BLACKS 33 6835 elder george WHITES 64 9026 BLACKS 33 7037 difference between w/b for geore w = 31 versus 35 difference between w/b for elder george = 26 versus 37 now, i would be willing to say that there is less difference in change for george w than the elder george ... in viewing the video ... i did not see that the person really said anything categorical about this ... he used the term "roughly" ... just depends if the VIEWER of the video and data wants to think that 4% verus 11% means "roughly" the same change ... or not thus, i don't think the moderator said anything really wrong ... At 04:27 PM 1/10/02 +, EugeneGall wrote: >The Gallup organization posted a video to explain why the the increase in >black's job approval for Bush is 'proportionate' to the increase among >whites. >Both increased by about 30% (60 to 90 for whites, mid thirties to roughly 70% >for blacks), so the increase is proportionate, not disproportionate, since >both >increases were about 30%. Unless I'm missing something, and I don't think I >am, this proportionate - disproportionate error is repeated and emphasized >several times in the video. > >http://www.gallup.com/poll/Multimedia/video/archived/2002/01/vr020108b.ram > >Gene Gallagher >UMASS/Boston > > >= >Instructions for joining and leaving this list, remarks about the >problem of INAPPROPRIATE MESSAGES, and archives are available at > http://jse.stat.ncsu.edu/ >= _ dennis roberts, educational psychology, penn state university 208 cedar, AC 8148632401, mailto:[EMAIL PROTECTED] http://roberts.ed.psu.edu/users/droberts/drober~1.htm = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
Proportionate vs. disproportionate
The Gallup organization posted a video to explain why the the increase in black's job approval for Bush is 'proportionate' to the increase among whites. Both increased by about 30% (60 to 90 for whites, mid thirties to roughly 70% for blacks), so the increase is proportionate, not disproportionate, since both increases were about 30%. Unless I'm missing something, and I don't think I am, this proportionate - disproportionate error is repeated and emphasized several times in the video. http://www.gallup.com/poll/Multimedia/video/archived/2002/01/vr020108b.ram Gene Gallagher UMASS/Boston = Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =
