Except for all those times the polls are wrong, for varying reasons. As for the ORER, as previously noted, those can be way off in terms of actual cars in service, so another variable.
So what you are saying Tim and Dave are saying is that their stats show us precisely how many box cars from each of the railroad in the US at the time being modeled should be present in your personal fleet of models in order to run consists that, over the year, match the national averages? And if you are only modeling one small segment of the larger railroad, say the GN in 1951, the percentages still count, you just reduce your box car fleet in numbers by the percentages so that you stay constant in the differences? So if there would be 100 CN cars on the GN system at that time, and you only have 90 cars total, you reduce the number proportionally? But what if your line is not part of the main line, but an important branch working the logging and mining routes in the Cascade foothills? I may be completely missing all this, but I am trying to understand how this would work on the average person's home layout, or is that not of any consequence?
To: STMFC@...: walterclark@...: Mon, 18 Aug 2008 21:52:50 +0000Subject: [STMFC] Re: Freight car distribution
--- In STMFC@..., "Bruce Smith" <smithbf@...> wrote:>> Folks,> > I grow weary of this. No one has answered Tony's challenge to provide> evidence that supports a "regional bias in boxcars" position. It seems> that any evidence that does not support this position is dismissed as> "absurd" or "biased" and opinion and hyperbole are used in lieu of data.> Many of the arguments that have been used about statistics are not based> in a sound understanding of the field. For example, deviations from the> mean are EXPECTED and do not invalidate the mean. Certainly,modeling the> deviations would be.... deviant!> > What I find truly remarkable is the wealth of DIFFERENT types ofdata that> seem to support the national fleet as a starting place for a model> representation. The Charles data is flawed at best, yet it supports the> model. Wheel reports from different locations support the model...> > -It ISN'T about individual trains (How often do we need to say this?)> -Individual trains may have very specific make-ups that varysignificantly> from the national averages.> -It is about a "fleet"> -That fleet will then fluctuate on the layout of the owner, providing> deviations from the mean... and modeling those deviations that almost> certainly occur in real life.> -It is a STARTING place - I have yet to hear anyone offer a different> starting place based on data other than their own opinion, and frankly,> I'd rather take my chances with the data ;^)> -The model DOES NOT preclude the use of oddballs, but it does INFORM the> modeler that these are oddballs.> > Over and out> Bruce> > Bruce Smith> Auburn, AL>Bruce, and all,What we have is the problem that always occurs when using statistics.Most people won't accept that a relatively small sample size canforecast much larger populations with extreme accuracy. Just listento the arguments after a national poll is released, where they polledonly a few thousand people and used that data to project within just afew percentage points of error what the entire Nation's population thinks.Tim's and Dave's analysis is for an entire year. Not every train, andnot every train in a single month. Neither Tim nor anyone else whoaccept Tim's and Dave's calculations are claiming that. It is thetotal of all box cars over an entire year. This can (not must, we allcan do what we darn well please on our own model railroads) help medecide which box car kits, and in what quantities, I need toreasonably represent the possible activity in my month of November1941 on my mythical short line that connects to the Southern Pacificin northern California. I had a professor in Graduate School who, in the Statistics class,always brought a cloth drawstring bag with 100 red and 100 black pokerchips to class. No matter what he was teaching, and no matter how bigor how small the numbers he was working with, a handful of chips fromthat bag was ALWAYS extremely close to what the calculations said. And grabbing 10 separate handfuls (counted and replaced in the bagbetween grabs) was ALWAYS RIGHT ON! This can be shown in any group of30 people. Even though there are a total of 366 possible birth dates,any somewhat random group of 30 people WILL ALMOST ALWAYS have twowith the same birth date.Intuitively it doesn't make sense, and that's what the naysayers arearguing. Yes, there are exceptions, and situations that don't matchthe calculations, but those exceptions and outlying situations aresmoothed out over time.Between Tim's and Dave's analysis, and Larry's Excel spreadsheet,along with a close-to-my-modeling-period ORER I can determine how manybox cars from what railroads I need to plan for, then adjust that asnecessary based on what kits are available to me.Is it perfect, and can I generate a single freight train thatperfectly matches a single freight train from Fraley? No, but thereis no way to come up with anything more accurate. Perfect? No, butbetter than the rest.Time stopped in November 1941Walter M. ClarkPullman, Washington, USA