I apologize for not having time to write dissertation type responses so I will be brief.
[snip] > MP: > Note that 4.5% of this group have doctorates. In > previous posts on this topic, estimates of the > percentage in the general population were calculated > using the Census* Community Survey data. In retreospect, > this is the wrong calculation to do, that is, one should > not take the number of Ph.D. estimated in the population > and divide it by the total number of people in the sample. > This does give one the percentage of the general population > that have Ph.D. but for purposes of comparison, the > denominator should the number of people between 24 to 94 > years of age, that age range of the richest groups. Children, > which would be included in the total sample number will > inflate the denominator and not provide the appropriate > number for comparison. In other words, to determine > whether the 4.5% of Ph.D.s in this richest group is an > *overrepresentation* or *underrepresentation* requires > one to compare 4.5% to the percentage of Ph.D.s in the > age range of 24 to 94 (excluding the richests). > > JC: > The tables Mike and I used earlier DO limit the denominator to adults > (18 and over or 25 and over in the case of Mike's earlier estimate of > .0125). So the earlier estimates hold. In my calculation of 1.25%, I'm pretty sure that I used total population as the denominator. I don't have the time right now but can anyone confirm or identify what the percentage of Ph.D.s are in the 24-94 range? > JC: > As Mike correctly notes, this is an excellent dataset for making some > good points in statistics (and other) classes. One such point might be > about restriction of range. As noted by Rick, we are looking at a tiny > proportion of the population defined by the very, very highest of > incomes. Is it reasonable to expect any relationship with such a > restricted sample/population? I briefly thought of restriction of range but consider the following: range of education level for Non-Richest: probably from some grade school to Ph.D. range of education level for the Richest 400: probably from some grade school to Ph.D. So, the educational levels for the two groups are quite similar though the overall frequency distribtuions may differ. range of networth in $Bil for Non-Richest: 0 to $1.3 Billion (there may be some negative networth individuals because of liabilities exceeding income/resources/investments/etc). or $1.3 Billion range of networth in $Bil for the Richest 400: $1.3 Bil to $57 Bill or $55.7 Billion. The ratio of the range for the Richest networth to the Nonrichest networth is 55.7/1.3 = 42.85, that is, the range for networth of the Richest is about 43 times that of the non-rich. Yes, there is restriction of range but it is with the Nonrich, thus any correlation based only on the Nonrich suffers from restriction of range. NOTE: it could be the case that any relationship between Networth and any other variable might involve "discontinuous regressions", that is, one type of regression holds for the relationship over one range of value (e.g., below $1 Billion in networth) and another regression model describes the relationship over other ranges of values (i.e., greater than $1 Billion). Perhaps someone should try to get the Forbes people to make their data on the richest people across the years publicly available (I don't know whether they do or not but can understand why they might not). It could make for some fascinating analysis. > Again, thanks to Mike P for taking the time. You're very welcome. -Mike Palij New York University m...@nyu.edu --- To make changes to your subscription contact: Bill Southerly (bsouthe...@frostburg.edu)
