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/ =================================================================
