Beginner requests for help on ANOVA and T-tests
Hello, I am a 16 year old student and a beginner to statistics. I'm lost. Currently I only have Microsoft Excel 97. And I would like to know the differences between the following ANOVA tests (in Excel): ANOVA Single Factor ANOVA Two-Factors with replication ANOVA Two-Factors without replication What do all these mean? Where and when should they be applied? And can anyone please use simple english terms to explain? I am only a beginner. What is one-way or two-way ANOVA? How about for T-Test? T-Test: Paired two samples for means T-Test: Two-sample assuming equal variances T-Test: Two-sample assuming unequal variances Also, can I use ANOVA instead of T-test when testing null hypothesis? Between 2 groups? Thanks for your help, Edmund Sent via Deja.com http://www.deja.com/ Before you buy. === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
need help
Dear SirI'm a researcher at Cairo University in the field of computer science.Due to my PHD I'm preparing a questionnaire. But the popular is very large.I classified it into 35 categories. All I need, is to determine the sample size. is it proportional to the popular size? How can I determine that sample size?Please I need your help.sahar salah[EMAIL PROTECTED]
Re: Statistics Help for Grad Students
People who do not know "what it means" should not be doing the statistics. -- Charles Madewell Reliability/Test Engineering, Systems/Materials Failure Analysis. Statistical Analysis, Design of Experiments, Regression/Modeling/Prediction. In article 8i6fnk$d29$[EMAIL PROTECTED], "Rudolph V. Richichi, Jr., Ph.D." [EMAIL PROTECTED] wrote: Attention graduate students, academics, and businesses. We help you design research, run statistical analyses, and get the most from your data. If you need help with data analysis, contact Statisticians.NET. We don't just analyze data. We explain what it means. Click the link below http://www.statisticians.net/ to find out more about our fees and services. Sent via Deja.com http://www.deja.com/ Before you buy. === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
Q: conditional probability
Any help, hints, direction etc. on this appreciated: I have a vector of measurements F, and two feature models L and R which give the pdf of a measurement Fi for that model i.e. P(Fi|Li) and P(Fi|Ri). Denoting the probability that there is a feature L at position i in the vector as P(Li) and similarly feature R at position j as P(Rj) I am interested in obtaining P(Li,Rj|F) i.e. the probability that there is feature L at position i and feature R at position j, given the vector F. The assumptions I will make are P(Li|F)=P(Li|Fi) and P(Ri|F)=P(Ri|Fi) i.e. the feature depends only on local value of the vector. What I will *not* assume is that P(Li) and P(Rj) are independent. i.e. the position of feature L influences that position of feature R. What I am looking for is an expression for P(Li,Rj|F) derived only from P(Fi|Li), P(Fj|Rj) and P(Li|Rj) or similar. P(Li,Rj|F) =P(Li|Rj,F)P(Ri,F) =P(Li|Rj,F)P(Ri,Fi) ...? Knowing that P(Li|F)=P(Li|Fi) can I simplify P(Li|Rj,F) further? Mark -- Mark Everingham Phone: +44 117 9545249 Room 1.15 Fax: +44 117 9545208 Merchant Venturers Building Email: [EMAIL PROTECTED] University of Bristol WWW: http://www.cs.bris.ac.uk/~everingm/ Bristol BS8 1UB, UK === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
Re: MANOVA
If some of your independent (predictor) variables are categorical, then the dots and zeros are not a problem but merely a refelction of what would be redundant parameters. At 01:00 AM 6/15/00 +0100, HAideren wrote: Hi, I have run a MANOVA and in the 'Parameter Estimates' section of the results, some of the cells are filled with a zero or a dot (.). Is there a way to overcome this problem? If no, should I run a different multivariate test and what would be the appropriate substitute test? Cheers. === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ === Paul R. Swank, PhD. Professor Advanced Quantitative Methodologist UT-Houston School of Nursing Center for Nursing Research Phone (713)500-2031 Fax (713) 500-2033 === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
Non Linear Regression, estimation of parameters for Richards Growth Curve
Hello all, I am trying to fit some data using the NLINFIT of MATLAB and using SAS. I am trying to fit the well know RICHARDS growth curve. It looks like y=a*(1-b*exp(-c*t))^d where we want to estimate the parameters a,b,c,and d. Here t is my input and is age squared while y is the weight of some animals. I choose my initial parameter starting values and they do converge and I get a wonderful looking fit with awesome residual plot. My question is this though. The estimate MATLAB finds for d is .44 which of course causes my predicted y's to be complex numbers when 1-b*exp(-c*t) is negative (very frequent in my case). What questions should this bring up. Is it ok to simply use the real parts of the numbers. That is what SAS did and when ploting the predicted curve to the original data I must say it looks just fine. Let me know your thoughts on the use of only the real parts of the complex values. Any advice and input will be much appreciated. Thanks , Mike === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
Re: Non Linear Regression, estimation of parameters for Richards , Growth Curve
1-b*exp(-c*t) is negative only if b*exp(-c*t) 1, which implies log(b) c*t, I think. Is this a reasonable circumstance in terms of the theory that led to the Richards growth curve? You say this occurs frequently in your data; since b and c are presumably constants for a given data set, "frequently" must refer to the varying values of t, which you described as age squared (and therefore always positive); these questionable values then must occur for small values of t. It might be interesting to inquire what the imaginary part of y-hat does as t increases to the point where log(b) = c*t. The phenomenon ought to be invariant with respect to the units of y and t. Is it? If you take t in days^2, do you get equivalent results to those you get when t is in hours^2 or months^2? And does it matter if y is in pounds or kilograms? Also presumably (I'm not familiar with this area) the parameters a, b, c, d are assumed to be positive numbers; do they turn out to be positive when estimated by this procedure? It all sounds rather as though the fitted value of b ( 0) is too large for the fitted value of c (also 0). Does that make sense? -- DFB. On Thu, 15 Jun 2000, Michael Henderson wrote: Hello all, I am trying to fit some data using the NLINFIT of MATLAB and using SAS. I am trying to fit the well know RICHARDS growth curve. It looks like y=a*(1-b*exp(-c*t))^d where we want to estimate the parameters a,b,c,and d. Here t is my input and is age squared while y is the weight of some animals. I choose my initial parameter starting values and they do converge and I get a wonderful looking fit with awesome residual plot. My question is this though. The estimate MATLAB finds for d is .44 which of course causes my predicted y's to be complex numbers when 1-b*exp(-c*t) is negative (very frequent in my case). What questions should this bring up. Is it ok to simply use the real parts of the numbers. That is what SAS did and when plotting the predicted curve to the original data I must say it looks just fine. Let me know your thoughts on the use of only the real parts of the complex values. Any advice and input will be much appreciated. Thanks , Mike Donald F. Burrill [EMAIL PROTECTED] 348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED] MSC #29, Plymouth, NH 03264 603-535-2597 184 Nashua Road, Bedford, NH 03110 603-471-7128 === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
Re: Beginner requests for help on ANOVA and T-tests (n SYSTAT97 --CAUTION)
Edmond-- You may want to use the REGRESSION program in Excel (WITH CAUTION). That way you can create your own models to do what YOU WANT TO DO. You might want to contact a statistician to help you use REGRESSION models. You don't need to use some of the Pre-Computer algorithms if you know who to create your models to answere YOUR QUESTIONS. The URL below has a few articles related to this message: http://www.ijoa.org/joeward/wardindex.html If the "packaged" algorithms answer the questions of interest, then you can use them. I am using Excel 97 with three high school students this summer. 2 Sophomores and 1 Senior in preparation for their Science Fair Research Projects. I usually use SYSTAT. However, these students already have Excel, so we are "testing" the use of REGRESSION in Excel. Incidentally, when you use REGRESSION models that need to: NOT HAVE THE Y-INTERCEPT TO PASS THROUGH ZERO, THE REGRESSION SUM OF SQUARES ARE NOT CORRECT. So be careful when you use REGRESSION in Excel 97. The Excel97 Error is due to the fact that the REGRESSION SUM OF SQUARES IS CALCULATED FROM THE "TOTAL SUM OF SQUARES" MINUS THE "RESIDUAL SUM OF SQUARES". THE "TOTAL SUM OF SQUARES" IS NOT CORRECT WHEN YOU INDICATED THAT YOU DO NOT WANT THE INTERCEPT TO PASS THROUGH THE ORIGIN. THE EXCEL PROGRAM USES THE "ADJUSTED SUM OF SQUARES" (REMOVING the REGRESSION SUM OF SQUARES ACCOUNTED FOR BY THE UNIT VECTOR (the "MEAN"). The REAL TOTAL SUM OF SQUARES IN THIS CASE SHOULD BE THE SUM OF SQUARES FOR THE DEPENDENT VARIABLE. Apparently the programmer of the REGRESSION procedure did not know how to compute the REAL TOTAL SUM OF SQUARES. As some of the users and creators of Statistical Software Packages frequently mention: "Using the statistical routines in Excel can be risky." Of course, ALL statistical packages should be used with caution. We have not had time to check on the Excel2000 to find out if it is still has the same problem. Keep in touch. -- JHW * Joe Ward * 167 East Arrowhead Dr. * San Antonio, TX 78228-2402 * Phone: 210-433-6575 * Fax: 210-433-2828 * Email: [EMAIL PROTECTED] * http://www.ijoa.org/joeward/wardindex.html * * Health Careers High School * 4646 Hamilton Wolfe * San Antonio, TX 78229 * Phone: 210-617-5400 * Fax: 210-617-5423 ** -Original Message- From: [EMAIL PROTECTED] [EMAIL PROTECTED] To: [EMAIL PROTECTED] [EMAIL PROTECTED] Date: Thursday, June 15, 2000 9:37 AM Subject: Beginner requests for help on ANOVA and T-tests Hello, I am a 16 year old student and a beginner to statistics. I'm lost. Currently I only have Microsoft Excel 97. And I would like to know the differences between the following ANOVA tests (in Excel): ANOVA Single Factor ANOVA Two-Factors with replication ANOVA Two-Factors without replication What do all these mean? Where and when should they be applied? And can anyone please use simple english terms to explain? I am only a beginner. What is one-way or two-way ANOVA? How about for T-Test? T-Test: Paired two samples for means T-Test: Two-sample assuming equal variances T-Test: Two-sample assuming unequal variances Also, can I use ANOVA instead of T-test when testing null hypothesis? Between 2 groups? Thanks for your help, Edmund Sent via Deja.com http://www.deja.com/ Before you buy. === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ === === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
Re: how to caculate the variance of x/y
Title: Re: how to caculate the variance of
x/y
@article{hink:1969,
Journal = {Biomtrka},
Volume = 56,
Pages = {635--639},
Author = {Hinkley, D. V.},
Title = {On the Ratio of Two Correlated Normal
Random Variables (Corr:
{V}57 P683)},
Year = 1969
}
@article{shan:1982,
Journal = {Ststcian},
Volume = 31,
Pages = {251--258},
Author = {Shanmugalingam, S.},
Title = {On the Analysis of the Ratio of Two
Correlated Normal
Variables},
Year = 1982
}
@article{cabu:spri:1990,
Journal = {CommStA},
Volume = 19,
Pages = {1157--1168},
Keywords = {Mellin transform; Ratio},
Author = {Cabuk, Serafettin and Springer, Melvin
D.},
Title = {Distribution of the Quotient of
Noncentral Normal Random
Variables},
Year = 1990
}
@article{schn:flei:1993,
Journal = {JStCmpSm},
Volume = 47,
Pages = {227--239},
Keywords = {Bivariate normal distribution; Uniform
distribution},
Author = {Schneeberger, H. and Fleischer, K.},
Title = {The Distribution of the Ratio of Two
Variables},
Year = 1993
}
At 13:17 -0500 06/15/2000, dz wrote:
Hi, anybody knows how to caculate the
variance of x/y? where x and y are two
independent variables with normal dis n(a1,b1) and
n(a2,b2) respectively.
Thank you.
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precision of 2 stage cluster sampling
I don't have my books available at the moment. Does anyone know of software or web page calculators where I can input 1) expected proportion (e.g., .5 or .8) 2) a total number of cases (e.g., 1000, 750, 500) 3) a number of PSUs (e.g., 300 to 75 by -25) 4) a confidence level .95 and get an estimate of the precision? Failing that would someone be so kind as to send the formula. === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
need help
subscribe EDSTAT-L sahar attia
No Subject
Due to my PHD I'm preparing a questionnaire. But the popular is very large.I classified it into 35 categories. All I need, is to determine the sample size. is it proportional to the popular size? How can I determine that sample size?Please I need your help.sahar salah
max the return
as many of us get (all to) closer and closer to retirement ... and, generally could kick ourselves more and more for not paying more serious attention to this matter earlier in our careers ... we face the fact that there are a limited number of years to make your money work for you ... before you have to start using it ... so, while this might not be a stat question per se (though we could probably make it one) ... i ask this for general advice ... if you feel your answer has no relevance to the list ... send me a personal note at ... mailto:[EMAIL PROTECTED] here is the question if you had 5- 10 years more ... in a salaried type of a position ... and, had a general choice between A. putting what cash you could muster into the best non tax sheltered investments you could (not the lowest nor the highest risk) ... where you will have to pay tax on your gains each year ... or B. putting that same amount (or maxing if you can) in employer deduction oriented tax sheltered investment strategies ... where you do NOT pay tax on the gains each year and lower your taxable income ... which of these two general ways will tend to benefit the average joe or sally ... the most? and, if there is not an answer to this ... tell me that too == dennis roberts, penn state university educational psychology, 8148632401 http://roberts.ed.psu.edu/users/droberts/droberts.htm === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
Re: how to caculate the variance of x/y
dz wrote: Hi, anybody knows how to caculate the variance of x/y? where x and y are two independent variables with normal dis n(a1,b1) and n(a2,b2) respectively. Thank you. This was posted by me only about two weeks ago. | | Hi Everyone. | | I've calculated the mean and variance of one variable (m1,v1) and the mean | and variance of a second variable (m2,v2). | So, my question is what is the variance of the quotient, response/stimulus, | in terms of v1 and v2 (and any other variable necessary). i.e, what is the | variance of m1/m2? | | There are no exact formulae for the qoutient of two random variables but | there is approximations. One comes from a Taylor series expansion of | m1/m2 around their means (mu1, mu2). Then take variances of both | sides and it becomes : | | Var(m1/m2) \approx= (mu1/mu2)^2 x [Var(m1)/(mu1)^2 + Var(m2)/(mu2)^2 + | Cov(m1, m2)/(mu1 x mu2)] + ... | Of course the big question is what is Cov(m1, m2). Well if m1 and m2 are | independent, which they may well be if the original variables say, y1 | and y2 were, then Cov() = 0. -- --- Julian Taylor Biometrics Adelaide University [EMAIL PROTECTED] --- === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
Re: Beginner requests for help on ANOVA and T-tests
I've not seen any particularly helpful responses to this post, so here's my attempt: On Thu, 15 Jun 2000 [EMAIL PROTECTED] wrote: Hello, I am a 16 year old student and a beginner to statistics. I'm lost. I'll assume you have access to some standard elementary statistics textbook. If this is not the case, let me know and I'll try translating any technical language in the sequel into, as you put it, simple English. Currently I only have Microsoft Excel 97. And I would like to know the differences between the following ANOVA tests (in Excel): ANOVA = analysis of variance (as I suppose you already know), a very general technique for testing the null hypothesis that the population means in several well-defined subgroups are all equal. For further elaboration see your text. ANOVA Single Factor = one-way ANOVA ANOVA Two-Factors with replication ANOVA Two-Factors without replication Both of these are variations on two-way ANOVA. I do not have Excel, so I will guess that "without replication" means that there is only one observation (or case) in each of the cells (subgroups) of the two-way design; and "with replication" means that there are more than one observation per cell. I would further guess that the number of cases per cell (in the "with replication" program) is required to be the same for all cells in the two-way design. (This constraint is not a logical requirement for two-way ANOVA, but it greatly simplifies both the programming required and the interpretation of results. It is not required for one-way ANOVA at all, generally.) What do all these mean? Read my replies above with your textbook in hand, open to the chapters on one-way and two-way ANOVA. Where and when should they be applied? Whenever it is useful to address the question, "Are the means equal?" for a set of subgroups (or cells, or categories) for which you have data, and it makes sense to consider the means (averages) of some variable in each of the subgroups. And can anyone please use simple english terms to explain? I am only a beginner. What is one-way or two-way ANOVA? If it is not yet clear from the above in conjunction with your text, perhaps you can identify an example in the text and transcribe it for us (An example you supply is likely to make more sense to you than a real or fictitious example one of us might be inclined to use, I suspect.) How about for T-Test? T-Test: Paired two samples for means T-Test: Two-sample assuming equal variances T-Test: Two-sample assuming unequal variances As the old song has it, T is for two [groups], and only two; for more than two groups, use ANOVA. "Paired samples" means that each observation in one sample corresponds to an observation in the other sample, and vice versa: as though you had taken measures on several persons in one sample, and the same measures on their identical twins in the other; or the one sample consists of "before" values and the other of "after" values, for the same persons. Hence there is a pair of values for each entity of interest (each pair of twins, or each person, respectively). "Two samples" would mean two independent samples -- different persons altogether in each group. Assuming the variancs of the two groups to be equal (or unequal) I take to be self-explanatory? Also, can I use ANOVA instead of T-test when testing null hypothesis? Between 2 groups? Yes. A one-way ANOVA on two groups is entirely equivalent to a t-test for two independent samples, assuming equal variances. (The square of the value of t calculated in the t-test is the value of F calculated in the ANOVA.) -- DFB. Donald F. Burrill [EMAIL PROTECTED] 348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED] MSC #29, Plymouth, NH 03264 603-535-2597 184 Nashua Road, Bedford, NH 03110 603-471-7128 === This list is open to everyone. Occasionally, less thoughtful people send inappropriate messages. Please DO NOT COMPLAIN TO THE POSTMASTER about these messages because the postmaster has no way of controlling them, and excessive complaints will result in termination of the list. For information about this list, including information about the problem of inappropriate messages and information about how to unsubscribe, please see the web page at http://jse.stat.ncsu.edu/ ===
