Re: Help for DL students in doing assignments
On Mon, 01 Oct 2001 16:51:27 GMT, Jon Miller <[EMAIL PROTECTED]> wrote: >"Dr. Fairman" wrote: > >> Dear DL Students, > >What's a DL student? "distance learning" student? = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
semi-studentized residual
Hello, I have a question regarding the so-called "semi-studentized residual," which is of the form (e_i)* = ( e_i - 0 ) / sqrt(MSE). Here, e_i is the ith residual, 0 is the mean of the residuals, and sqrt(MSE) means the square root of MSE. Now, if I understand correctly, the population simple linear regression model assumes that the E_i, the error terms, are independent and identically distributed random variables with N(0, sigma^2). My question is, are semi-studentized residuals not fully studentized because MSE is not the variance of all the residuals? It seems like MSE would be the variance of the residuals, unless of course the residuals from the sample data are not independent and identically distributed random variables. If not, each residual may have its own variance, in which case we would have to find this and studentize each residual by its own standard error? I am not sure if I am thinking about this in the right way. Also, if the E_i are iid random variables, does this mean that the observations Y_i are iid random variables within a particular level of X? (I know that in general the Y_i are not iid r.v. since they have different means depending on the level of X). I hope these questions make sense. Thank you for your help. ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
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Logistic Regression vs Chi Square test in the following scenario
Hi I have a question to the group here. Let's say I have two variables: y is the dependent variable, x is the independent variable. X Y --- 0 1 1 1 1 1 1 0 0 0 0 1 1 0 1 1 etc etc. Both variables are binary and discrete. I want to see if there is a relation between x and y. Is it possible to use logistic regression analysis in this case and generate a p value from a F statstic? Or should I be using a chisquare test? Thanks, Nick = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: optimal sample size
> I think I am trying to say, gently, that your basic question doesn't > make very good sense to me; and it did not, to Dennis, either. > "Optimal" is one problematic word. Another problem is that > you seem to ask about all research, in all of the world > It might be a clever way to attack 'sample size', but I think > that hasn't been done. Thanks for your advise. I see that the question is probably a little bit overloaded and that optimal is not a good definition. But isn't there something that determines the sample size of all statistical techniques? I remember having read something a long time ago, that sample size of all statistical techniques are influenced by alpha risk, power and effect size. Is this wrong or is not applicable to my question? = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: optimal sample size
> what is the MINIMAL n needed to accomplish these ends" ... that might be optimal if you are looking for the > smallest n you can get by with ... but, optimal does not have to be defined > as such ... Thanks for your comments. To be honest, for me the term "opitmal" (which seems not to be a very good term) reffered completely to the task of minimizing sample size without risking to not be able to reject the "null hypothesis". What could be another definition of optimal in connection with sample size? = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Help for DL students in doing assignments
> Dear DL Students, > > I have Ph.D. degree in mathematics, physics, electrical engineering, > computer science. Can you please post details of your 3 PhDs! Nim. = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Help for DL students in doing assignments
Jon Miller <[EMAIL PROTECTED]> writes: > What's a DL student? "Distance Learning", I'd imagine. -- Rich Carreiro[EMAIL PROTECTED] = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: They look different; are they really?
Be careful of the move from data to conclusion! You say "whether one class really is learning the subject better than the other, and by how much?" Even assuming the test yields a good measure of how well the students know the material (which should be investigated, rather than assumed), it isn't telling you whether students have learned more from the class itself, unless you assume all students started from the same place. As I gather is common in this field, the problem isn't statistics per se, but framing questions that can be answered by the kind of data you can get. >Stan Brown wrote: > >> Another instructor and I gave the same exam to our sections of a >> course. Here's a summary of the results: >> >> Section A: n=20, mean=56.1, median=52.5, standard dev=20.1 >> Section B: n=23 mean=73.0, median=70.0, standard dev=21.6 >> >> Now, they certainly _look_ different. (If it's of any valid I can >> post the 20+23 raw data.) If I treat them as samples of two >> populations -- which I'm not at all sure is valid -- I can compute >> 90% confidence intervals as follows: >> >> Class A: 48.3 < mu < 63.8 >> Class B: 65.4 < mu < 80.9 >> >> As I say, I have major qualms about whether this computation means >> anything. So let me pose my question: given the two sets of results >> shown earlier, _is_ there a valid statistical method to say whether >> one class really is learning the subject better than the other, and >> by how much? Jill Binker Fathom Dynamic Statistics Software KCP Technologies, an affiliate of Key Curriculum Press 1150 65th St Emeryville, CA 94608 1-800-995-MATH (6284) [EMAIL PROTECTED] http://www.keypress.com http://www.keycollege.com __ = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: They look different; are they really?
were these two different sections at the same class time? that is ... 10AM on mwf? if not ... then there can be all kinds of reasons why means would be this different ... nonewithstanding one or two real deviant scores in either section ... could also be different quality in the instruction ... all kinds of things of course, if you opted for 95 or 99% cis, the non overlap would be greater ... what is the purpose of doing this in the first place? do not the mean differences really suggest that there is SOMEthing different about the two groups ... ? or ... at least something different in the overall operation of the course in these two sections? At 02:33 PM 10/1/01 -0300, Gus Gassmann wrote: >Stan Brown wrote: > > > Another instructor and I gave the same exam to our sections of a > > course. Here's a summary of the results: > > > > Section A: n=20, mean=56.1, median=52.5, standard dev=20.1 > > Section B: n=23 mean=73.0, median=70.0, standard dev=21.6 > > > > Now, they certainly _look_ different. (If it's of any valid I can > > post the 20+23 raw data.) If I treat them as samples of two > > populations -- which I'm not at all sure is valid -- I can compute > > 90% confidence intervals as follows: > > > > Class A: 48.3 < mu < 63.8 > > Class B: 65.4 < mu < 80.9 == dennis roberts, penn state university educational psychology, 8148632401 http://roberts.ed.psu.edu/users/droberts/drober~1.htm = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Looking for Presenters at the ISF 2002 in Dublin
I am looking for interested parties to present next June in the field of "Intermittent Demand" Forecasting. Of course, if you have an interest in another area I will be glad to pass your name on to for consideration. If you are interested send me an e-mail at [EMAIL PROTECTED] stating a synopsis of what your 45 minute speech would focus on. This conference is more of academic group, but applications of methodologies is also welcomed. See http://www.isf2002.org/ for more info. The conference is 6/23-6/26. They always have well organized functions with good eats and tours. Tom Reilly = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: They look different; are they really?
Stan Brown wrote: > Another instructor and I gave the same exam to our sections of a > course. Here's a summary of the results: > > Section A: n=20, mean=56.1, median=52.5, standard dev=20.1 > Section B: n=23 mean=73.0, median=70.0, standard dev=21.6 > > Now, they certainly _look_ different. (If it's of any valid I can > post the 20+23 raw data.) If I treat them as samples of two > populations -- which I'm not at all sure is valid -- I can compute > 90% confidence intervals as follows: > > Class A: 48.3 < mu < 63.8 > Class B: 65.4 < mu < 80.9 > > As I say, I have major qualms about whether this computation means > anything. So let me pose my question: given the two sets of results > shown earlier, _is_ there a valid statistical method to say whether > one class really is learning the subject better than the other, and > by how much? Before you jump out of a window, you should ask yourself if there is any reason to suspect that the samples should be homogeneous (assuming equal learning). Remember that the students are often self-selected into the sections, and the reasons for selecting one section over the other may well be correlated with learning styles and/or scholastic achievements. --- gus gassmann ([EMAIL PROTECTED]) "When in doubt, travel." Remove NOSPAM in the reply-to address = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: optimal sample size
On Mon, 1 Oct 2001 12:23:28 +0200, "Bernhard Kuster"
<[EMAIL PROTECTED]> wrote:
> Hi
>
> I am interessted in the question of optimal sample size in general, not for
> a special statistical technique.
(a) There was a notable 1974 article on "Believability when N=1" and
here is an academic webpage on the subject. It includes good
references.
http://www-personal.umich.edu/~hinderer/scrdoutline.html
(b) Richard Peto's writing may have been the impetus behind
one or two "mega-studies." He pointed out that by having
a clear-cut, randomized treatment ("treatment
given within x hours of a heart attack") and an unambiguous
outcome ("still alive after 30 days"), it should be possible
to combine the experience of hundreds of hospitals,
and 10,000's of patients. And it was done. I think that the
randomization was in there, and was possible because
no one had great faith in the treatment. The huge N was
a *necessary* sample size because of the small size of the
expected effect as an odds ratio, and the small fraction of
people who would be mortalities-who-might-be-saved.
There you have the extremes of what is optimum for
"sample size in general, not for a special technique."
>
> My questions: (1) What do I have to keep in mind if I compute optimal sample
> size, what is relevant? (2) What are the classic studies and who has highly
> influenced the subject? (3) What are the problems discussed right now by the
> scientific community? (4) What are the relevant journals and is there some
> information on the web?
I think you might find some issues included in Robert P. Abelson,
"Statistics as principled argument."
I think I am trying to say, gently, that your basic question doesn't
make very good sense to me; and it did not, to Dennis, either.
"Optimal" is one problematic word. Another problem is that
you seem to ask about all research, in all of the world
It might be a clever way to attack 'sample size', but I think
that hasn't been done.
--
Rich Ulrich, [EMAIL PROTECTED]
http://www.pitt.edu/~wpilib/index.html
=
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Re: Help for DL students in doing assignments
"Dr. Fairman" wrote: > Dear DL Students, What's a DL student? Jon Miller = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re:
Just a reminder, folks - The Usenet group is linked to a mailing list. If you really want to Unsubscribe from the mailing list, do NOT post your request to the group's address for Questions. Please heed the message which is listed AT THE BOTTOM OF EVERY MAIL-LIST MESSAGE - and read those instructions which tell you a different address. On 1 Oct 2001 07:47:01 -0700, [EMAIL PROTECTED] (Charles Blaich) wrote: - his message unsubscribe [ ... snip, tag ] = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ = -- end message -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
They look different; are they really?
Another instructor and I gave the same exam to our sections of a course. Here's a summary of the results: Section A: n=20, mean=56.1, median=52.5, standard dev=20.1 Section B: n=23 mean=73.0, median=70.0, standard dev=21.6 Now, they certainly _look_ different. (If it's of any valid I can post the 20+23 raw data.) If I treat them as samples of two populations -- which I'm not at all sure is valid -- I can compute 90% confidence intervals as follows: Class A: 48.3 < mu < 63.8 Class B: 65.4 < mu < 80.9 As I say, I have major qualms about whether this computation means anything. So let me pose my question: given the two sets of results shown earlier, _is_ there a valid statistical method to say whether one class really is learning the subject better than the other, and by how much? -- Stan Brown, Oak Road Systems, Cortland County, New York, USA http://oakroadsystems.com My reply address is correct as is. The courtesy of providing a correct reply address is more important to me than time spent deleting spam. = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: They look different; are they really?
Stan Brown wrote: > _is_ there a valid statistical method to say whether > one class really is learning the subject better than the other, and > by how much? If your question is, "Do the means disagree by more than one would expect if the 43 individual grades were partitioned into two sets of 20 and 23 at random?", the answer is yes. = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: What is a confidence interval?
Ronald Bloom wrote: > > Jerry Dallal <[EMAIL PROTECTED]> wrote: > > John Jackson wrote: > >> > >> this is the second time I have seen this word used: "frequentist"? > > > Since Radford Neal has already given an excellent explanation, > > let me add... > > > A roulette wheel comes up with a red number 10 times in a row. When > > deciding how to place his/her next bet... > > > The person on the street bets black, "Because it's got to come up > > eventually." > > > The frequentist doesn't care, "Because red and black occur at random > > with equal chances and past history doesn't matter." > > > The Bayesian bets red, "Because there's something strange going on > > here!" > > *I'd* bet The person on the street *also* bets red, "Because it > looks like there's something strange going on!" 10? Did I type 10? The "10" key is s close to the "5" key. I meant "5". Sorry for the confusion! :-) = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
edstat@jse.stat.ncsu.edu
unsubscribe -- Charles Blaich Daniel F. Evans Associate Professor of Social Science Special Assistant to the Dean for Strategic Initiatives Wabash College Crawfordsville, IN 47933 = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
"Pluma y Fuente" Nº 177 del 01/10/2001.
__ Logos Traducciones - www.logos.it __ "Pluma y Fuente" del 01/10/2001. Edición Nº 177. Informaciones seleccionadas por Reporters Online EDITORIAL DEL DÍA. Histórica Resolución del Consejo de Seguridad ONU contra el terrorismo, por ahora limitada a las cuestiones de los flujos financieros; pero, desde hace 30 años otras resoluciones no pasan. http://www.reportersonline.org/owa-k/press.parentesi.vedi?Hlingua=es&Hcodice=335 ÁFRICA - George Bush pide a Mauritania su adhesión a la alianza antiterrorista mientras el Presidente de Kenia, Arap Moi, encabeza la Marcha contra los terroristas. http://www.reportersonline.org/owa-k/press.news_es.print?H=Africa&D=01-OCT-2001&L=es ASIA-PACÍFICO - La delegación de Ulemas de Pakistán que viajó a Afganistán para tratar con los Talibán una posible cooperación en la lucha antiterrorista fracasó completamente. - Los Talibán dicen: «Tenemos bajo control a Osama bin-Laden». La inmediata respuesta de los Estados Unidos: «No nos interesa y no hay nada que negociar». - Los Gobiernos de Siria, Iraq y Argelia, con matices diferentes, coinciden en afirmar que cualquiera acción militar debe ser aprobada por las Naciones Unidas. - No se presenta fácil la tarea y el proyecto del ex rey de Afganistán, exiliado en Roma desde hace 28 años, para elaborar una plataforma política unitaria anti-Talibán. - Comenzó hoy el juicio contra el ex Presidente filipino Joseph Estrada por corrupción y otros delitos. El ex mandatario de encuentra detenido desde hace varios meses. http://www.reportersonline.org/owa-k/press.news_es.print?H=Asia&D=01-OCT-2001&L=es EUROPA - Silvio Berlusconi: ´´Lamento que alguna palabra sacada de contexto haya sido malinterpretada y haya podido herir la sensibilidad de mis amigos árabes y musulmanes´´. - El Primer Ministro británico, al parecer el único gobernante occidental que ha visto las pruebas contra bin-Laden, afirma: «Son incuestionables y unívocas». http://www.reportersonline.org/owa-k/press.news_es.print?H=Europa&D=01-OCT-2001&L=es IBEROAMÉRICA - A pesar de las críticas Vicente Fox, Presidente de México, reitera el apoyo irrestricto a los EE.UU. y se declara optimista frente a las relaciones bilaterales futuras. - Consuelo Araujo Noguera ex Ministro de la Cultura de Colombia, secuestrada hace una semana por las FARC fue asesinada por sus secuestradores. Crimen inaudito. - Después de las primeras protestas contra su Gobierno, el Presidente de Perú, Alejandro Toledo, aseguró ayer que la situación socio-económica del país mejorará. «Hay buenas esperanzas», dijo. - Cuarto discurso en una semana del Presidente Fidel Castro que pide impedir más violencias y castigar a los terroristas con procesos en tribunales imparciales. - El Presidente de Colombia, después del secuestro y asesinato de una ex Ministro de Cultura, «congela» las negociaciones de paz con las FARC. http://www.reportersonline.org/owa-k/press.news_es.print?H=Iberoamerica&D=01-OCT-2001&L=es INTERNET - En estos días se recuerda el tercer decenio de la existencia del correo electrónico, ´´e-mail´´, que se ha convertido en un instrumento imprescindible. http://www.reportersonline.org/owa-k/press.news_es.print?H=Internet&D=01-OCT-2001&L=es LENGUAS - UNA BUENA PALABRA: (1) La lengua china en español y los sistemas Pinyin y Wade-Giles. http://www.reportersonline.org/owa-k/press.news_es.print?H=Lingue&D=01-OCT-2001&L=es MEDIO ORIENTE - Peres y Arafat, a través de sus enviados especiales, preparan el segundo encuentro concordado la semana pasada para consolidar la tregua. - Shimon Peres acusa al Vice jefe de las FF.AA. de Israel de organizar y dirigir planes para asesinar al Presidente de la Autoridad Palestina, Yaser Arafat. Ayer domingo nuevas víctimas palestinas. - Esta mañana explota un coche-bomba en la calle Belén de Jerusalén. En el atentado resultaron heridas dos personas que fueron atendidas en el lugar de los hechos. http://www.reportersonline.org/owa-k/press.news_es.print?H=Medio&D=01-OCT-2001&L=es MUNDO - Hoy, en la apertura de las Sesiones de la Asamblea General de la ONU, dedicadas al tema del terrorismo, interviene el Alcalde de Nueva York, Rudolph Giuliani. - Comienza hoy la Asamblea general de la ONU número 56 para discutir una estrategia global contra el terrorismo iinternacional aprobando nuevas Resoluciones. - El Papa abre los trabajos del Sínodo de obispos para discutir sobre el primado del Pontífice e invita a todos a rezar por la paz, contra el terrorismo. http://www.reportersonline.org/owa-k/press.news_es.print?H=Mondo&D=01-OCT-2001&L=es NORTEAMÉRICA - Altos oficiales del Pentágono afirman que la llamada «alianza antiterrorista» cuenta con la adhesión de más de 100 naciones de todo el mundo. - Sigue disminuyendo la cifra de las personas muertas y desaparecidas en los atentados. El Alcalde de Nueva York ahora dice que son 5.756. - En estos 20 días de investigaciones por los atentados contra los EE.UU: las autoridad
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Re: optimal sample size
of course. the most important issue is ... what do you mean by optimal? if you can specify what the purpose of the sampling project is ... the parameter to be estimated, within what margin of error, etc. ... then you might be able to answer the question ... "what is the MINIMAL n needed to accomplish these ends" ... that might be optimal if you are looking for the smallest n you can get by with ... but, optimal does not have to be defined as such ... At 12:23 PM 10/1/01 +0200, Bernhard Kuster wrote: >Hi > >I am interessted in the question of optimal sample size in general, not for >a special statistical technique. > >My questions: (1) What do I have to keep in mind if I compute optimal sample >size, what is relevant? (2) What are the classic studies and who has highly >influenced the subject? (3) What are the problems discussed right now by the >scientific community? (4) What are the relevant journals and is there some >information on the web? > >Can anybody advise on one or more of these questions? Thanks a lot! > >Bernhard > > > >= >Instructions for joining and leaving this list and remarks about >the problem of INAPPROPRIATE MESSAGES 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 and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
optimal sample size
Hi I am interessted in the question of optimal sample size in general, not for a special statistical technique. My questions: (1) What do I have to keep in mind if I compute optimal sample size, what is relevant? (2) What are the classic studies and who has highly influenced the subject? (3) What are the problems discussed right now by the scientific community? (4) What are the relevant journals and is there some information on the web? Can anybody advise on one or more of these questions? Thanks a lot! Bernhard = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
K-Means QuickClusteranalysis (OptimalSolution)
Hello, i look for a good way to find the optimal number of cluster for a special problem ! Is it right to sum the distanceValues^2 and look for the point where these sumOfEuclideanDistance have the most lost from one to the next ClusterSolution ? P.S. I hope my english is not to bad ;-( thanks for advance & regards christian = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
