Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-30 Thread Art Kendall
In my experience, students benefit from the individual and group _production_ of summaries, syndicate notes, and cheat sheets. Reviewing the summaries produced by students gives a teacher feedback on what is or is not understood, and whether the relative emphasis of the lessons _as received_ is

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-27 Thread Herman Rubin
In article [EMAIL PROTECTED], Alan McLean [EMAIL PROTECTED] wrote: Herman Rubin wrote: In article [EMAIL PROTECTED], Alan McLean [EMAIL PROTECTED] wrote: Robert J. MacG. Dawson wrote: Alan McLean wrote: The p value is a direct measure of 'strength of evidence'. and Lise DeShea

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-26 Thread Herman Rubin
In article [EMAIL PROTECTED], Paul W. Jeffries [EMAIL PROTECTED] wrote: Robert Dawson said that one of his approaches to dealing with z test is to treat it as a historical anecdote. I like that approach and must give it a try. It is almost the other way around. The z test comes up as an

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-26 Thread Herman Rubin
In article [EMAIL PROTECTED], Robert J. MacG. Dawson [EMAIL PROTECTED] wrote: Paul W. Jeffries wrote: What are list members views on teaching students to use tables. In the computer age, tables are an anachronism. The vast

p- values Was: Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-26 Thread Herman Rubin
In article [EMAIL PROTECTED], Lise DeShea [EMAIL PROTECTED] wrote: Alan McLean wrote: ... In general, I emphasise the use of p values - in many ways it is a more natural way than using critical values to carry out a test. The p value is a direct measure of 'strength of evidence'. I

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-26 Thread Alan McLean
Herman Rubin wrote: In article [EMAIL PROTECTED], Alan McLean [EMAIL PROTECTED] wrote: Robert J. MacG. Dawson wrote: Alan McLean wrote: The p value is a direct measure of 'strength of evidence'. and Lise DeShea responded: ...

RE: Student's t vs. z tests

2001-04-26 Thread Mark W. Humphries
On 24 Apr 2001, Mark W. Humphries wrote: I concur. As I mentioned at the start of this thread, I am self-learning statistics from books. I have difficulty telling what is being taught as necessary theoretical 'scaffolding' or 'superceded procedures', and what one would actually apply in a

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-26 Thread Herman Rubin
In article [EMAIL PROTECTED], Alan McLean [EMAIL PROTECTED] wrote: Robert J. MacG. Dawson wrote: Alan McLean wrote: The p value is a direct measure of 'strength of evidence'. and Lise DeShea responded: ... There is certainly no contradiction. A

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-25 Thread Alan McLean
I agree - although students do need tables in (written) exams... But we use a computer program called Tuteman in our teaching and testing, so the natural way to find critical values or p-values is via the computer - we use Excel mainly. In general, I emphasise the use of p values - in many

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-25 Thread Lise DeShea
Alan McLean wrote: ... In general, I emphasise the use of p values - in many ways it is a more natural way than using critical values to carry out a test. The p value is a direct measure of 'strength of evidence'. I disagree. The p-value may be small when a study has enormous power yet a

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-25 Thread Robert J. MacG. Dawson
Alan McLean wrote: The p value is a direct measure of 'strength of evidence'. and Lise DeShea responded: I disagree. The p-value may be small when a study has enormous power yet a small effect size. A p-value by itself doesn't say much. I don't think there's actually a

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-25 Thread Alan McLean
Robert J. MacG. Dawson wrote: Alan McLean wrote: The p value is a direct measure of 'strength of evidence'. and Lise DeShea responded: I disagree. The p-value may be small when a study has enormous power yet a small effect size. A p-value by itself doesn't say much.

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-25 Thread jim clark
Hi On 25 Apr 2001, Alan McLean wrote: I agree - although students do need tables in (written) exams... But we use a computer program called Tuteman in our teaching and testing, so the natural way to find critical values or p-values is via the computer - we use Excel mainly. In general, I

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-25 Thread Robert J. MacG. Dawson
Paul W. Jeffries wrote: What are list members views on teaching students to use tables. In the computer age, tables are an anachronism. The vast majority of students will never use a t table. Were it only so...

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-25 Thread dennis roberts
as for the use of t tables ... or any other ... 1. one issue is can the student USE the table ... that is, you specify some from the table and you want to know if they can find it 2. another issue is what the student knows about what happens in the table as df changes 3. another issue is

Re: Artifacts in stats: (Was Student's t vs. z tests)

2001-04-25 Thread Robert J. MacG. Dawson
dennis roberts wrote: as for the use of t tables ... or any other ... 1. one issue is can the student USE the table ... that is, you specify some from the table and you want to know if they can find it Yes. That is, in my experience, students, small dogs, and most white

Artifacts in stats: (Was Student's t vs. z tests)

2001-04-24 Thread Paul W. Jeffries
Robert Dawson said that one of his approaches to dealing with z test is to treat it as a historical anecdote. I like that approach and must give it a try. But this approach made me think about artifacts in statistics. What are list members views on teaching students to use tables. In the

Re: FW: Student's t vs. z tests

2001-04-24 Thread jim clark
Hi On 24 Apr 2001, Mark W. Humphries wrote: I concur. As I mentioned at the start of this thread, I am self-learning statistics from books. I have difficulty telling what is being taught as necessary theoretical 'scaffolding' or 'superceded procedures', and what one would actually apply in a

Re: FW: Student's t vs. z tests

2001-04-24 Thread dennis roberts
I think that reading the scientific literature would disabuse one about the limited application of statistical significance. My students tell me that learning about statistical inference greatly increases their capacity to read primary literature. Perhaps it is different in your discipline.\

Re: Student's t vs. z tests

2001-04-23 Thread Alan Zaslavsky
Date: Fri, 20 Apr 2001 13:02:57 -0500 From: Jon Cryer [EMAIL PROTECTED] Could you please give us an example of such a situation? Consider first a set of measurements taken with a measuring instrument whose sampling errors have a known standard deviation (and approximately normal

Re: Student's t vs. z tests

2001-04-23 Thread Jon Cryer
These examples come the closest I have seen to having a known variance. However, often measuring instruments, such as micrometers, quote their accuracy as a percentage of the size of the measurement. Thus, if you don't know the mean you also don't know the variance. Jon Cryer At 09:28 AM

Re: Student's t vs. z tests

2001-04-23 Thread Will Hopkins
At 1:18 PM -0500 23/4/01, Jon Cryer wrote: These examples come the closest I have seen to having a known variance. However, often measuring instruments, such as micrometers, quote their accuracy as a percentage of the size of the measurement. Thus, if you don't know the mean you also don't know

Re: Student's t vs. z tests

2001-04-23 Thread Robert J. MacG. Dawson
Jon Cryer wrote: These examples come the closest I have seen to having a known variance. However, often measuring instruments, such as micrometers, quote their accuracy as a percentage of the size of the measurement. Thus, if you don't know the mean you also don't know the variance.

Re: Student's t vs. z tests

2001-04-23 Thread dennis roberts
the fundamental issue here is ... is it reasonably to expect ... that when you are making some inference about a population mean ... that you will KNOW the variance in the population? i suspect that the answer is no ... in all but the most convoluted cases ... or, to say it another way ...

Re: Student's t vs. z tests

2001-04-23 Thread Robert J. MacG. Dawson
dennis roberts wrote: the fundamental issue here is ... is it reasonably to expect ... that when you are making some inference about a population mean ... that you will KNOW the variance in the population? No, Dennis, of course it isn't - at least in the social sciences and

Re: Student's t vs. z tests

2001-04-23 Thread Alan McLean
I can't help but be reminded of learning to ride a bicycle. 99.% of people ride one with two wheels (natch!) - but many children do start to learn with training wheels.. Alan dennis roberts wrote: the fundamental issue here is ... is it reasonably to expect ... that when you are

Re: Student's t vs. z tests

2001-04-21 Thread jim clark
Hi On Fri, 20 Apr 2001, dennis roberts wrote: At 10:58 AM 4/20/01 -0500, jim clark wrote: What does a t-distribution mean to a student who does not know what a binomial distribution is and how to calculate the probabilities, and who does not know what a normal distribution is and how to

Student's t vs. z tests

2001-04-20 Thread Alan Zaslavsky
(This note is largely in support of points made by Rich Ulrich and Paul Swank.) I disagree with the claim (expressed in several recent postings) that z-tests are in general superseded by t-tests. The t-test (in simple one-sample problems) is developed under the assumption that independent

Re: Student's t vs. z tests

2001-04-20 Thread Jon Cryer
Alan: Could you please give us an example of such a situation? "Consider first a set of measurements taken with a measuring instrument whose sampling errors have a known standard deviation (and approximately normal distribution)." Jon At 01:10 PM 4/20/01 -0400, you wrote: (This note is

Re: Student's t vs. z tests

2001-04-20 Thread Jon Cryer
Alan: I don't understand your comments about the estimation of a proportion. It sounds to me as if you are using the estimated standard error. (Surely you are not assuming a known standard error.) You are presumably, also using the normal approximation to the binomial (or perhaps the

Re: Student's t vs. z tests

2001-04-20 Thread dennis roberts
alan and others ... perhaps what my overall concern is ... and others have expressed this from time to time in varying ways ... is that 1. we tend to teach stat in a vacuum ... 2. and this is not good the problem this creates is a disconnect from the question development phase, the measure

Re: Student's t vs. z tests

2001-04-20 Thread dennis roberts
nice note mike Impossible? No. Requiring a great deal of effort on the part of some cluster of folks? Definitely! absolutely! There is some discussion of this very possibility in Psychology, although I've yet to see evidence of fruition. A very large part of the problem, in my mind, is

Re: Student's t vs. z tests

2001-04-19 Thread Paul Swank
However, rather than do that why not right on to F? Why do t at all when you can do anything with F that t can do plus a whole lot more? At 10:58 PM 4/19/01 -0400, you wrote: >students have enough problems with all the stuff in stat as it is ... but, >when we start some discussion about sampling

Re: Student's t vs. z tests

2001-04-19 Thread dennis roberts
At 10:39 AM 4/19/01 -0500, Paul Swank wrote: However, rather than do that why not right on to F? Why do t at all when you can do anything with F that t can do plus a whole lot more? don't necessarily disagree with this but, i don't ever see in the literature in two group situations comparing

Re: Student's t vs. z tests

2001-04-19 Thread Robert J. MacG. Dawson
Paul Swank wrote: However, rather than do that why not right on to F? Why do t at all when you can do anything with F that t can do plus a whole lot more? Because the mean, normalized using the hypothesized mean and the observed standard deviation, has a t distribution and not an F

Re: Student's t vs. z tests

2001-04-19 Thread Paul Swank
I agree. I still teach the t test also because of this, but at the same time I realize that what goes around, comes around, so what we are doing is ensuring that we will continue to see t tests in the literature. However, I find linear models easier to teach (once I erase the old stuff from their

Re: Student's t vs. z tests

2001-04-19 Thread Paul Swank
They are more than just related. One is a natural extension of the other just as chi-square is a natural extension of Z. With linear models, one can begin with a simple one sample model and build up to multiple factors and covariates using the same basic framework, which I find easier to make

Re: Student's t vs. z tests

2001-04-19 Thread Paul Swank
I agree. I normally start inference by using the binomial and then then the normal approximation to the binomial for large n. It might be best to begin all graduate students with nonparametric statistics followed by linear models. Then we could get them to where they can do something interesting

Re: Student's t vs. z tests

2001-04-19 Thread dennis roberts
At 04:42 PM 4/19/01 +, Radford Neal wrote: In article [EMAIL PROTECTED], dennis roberts [EMAIL PROTECTED] wrote: I don't find this persuasive. nor the reverse ... since we have NO data on any of this ... only our own notions of how it MIGHT play itself out inside the heads of students I

Re: Student's t vs. z tests

2001-04-19 Thread Radford Neal
In article [EMAIL PROTECTED], dennis roberts [EMAIL PROTECTED] wrote: students have enough problems with all the stuff in stat as it is ... but, when we start some discussion about sampling error of means ... for use in building a confidence interval and/or testing some hypothesis ... the

Re: Student's t vs. z tests

2001-04-19 Thread dennis roberts
At 11:47 AM 4/19/01 -0500, Christopher J. Mecklin wrote: As a reply to Dennis' comments: If we deleted the z-test and went right to t-test, I believe that students' understanding of p-value would be even worse... i don't follow the logic here ... are you saying that instead of their

Re: Student's t vs. z tests

2001-04-19 Thread Jon Cryer
Why not introduce hypothesis testing in a binomial setting where there are no nuisance parameters and p-values, power, alpha, beta,... may be obtained easily and exactly from the Binomial distribution? Jon Cryer At 01:48 AM 4/20/01 -0400, you wrote: At 11:47 AM 4/19/01 -0500, Christopher J.

Re: Student's t vs. z tests

2001-04-19 Thread Alan McLean
All of your observations about the deficiencies of data are perfectly valid. But what do you do? Just give up because your data are messy, and your assumptions are doubtful and all that? Go and dig ditches instead? You can only analyse data by making assumptions - by working with models of the

Re: Student's t vs. z tests

2001-04-17 Thread Jerry Dallal
"Mark W. Humphries" wrote: If I understand correctly the t test, since it takes into account degrees of freedom, is applicable whatever the sample size might be, and has no drawbacks that I could find compared to the z test. Have I misunderstood something? From my class notes (which, in

Re: Student's t vs. z tests

2001-04-17 Thread Joe Ward
16, 2001 3:43 PM Subject: Re: Student's t vs. z tests Mark W. Humphries [EMAIL PROTECTED] wrote: Hi, I am attempting to self-study basic multivariate statistics using Kachigan's "Statistical Analysis" (which I find excellent btw). Perhaps someone would be kind enough to cl

RE: Student's t vs. z tests

2001-04-16 Thread Wuensch, Karl L.
If you knew the population SD (not likely if you are estimating the population mean), you would have more power with the z statistic (which requires that you know the population SD rather than estimating it from the sample) than with t. -Original Message- If I understand correctly the t

Re: Student's t vs. z tests

2001-04-16 Thread Eric Bohlman
Mark W. Humphries [EMAIL PROTECTED] wrote: Hi, I am attempting to self-study basic multivariate statistics using Kachigan's "Statistical Analysis" (which I find excellent btw). Perhaps someone would be kind enough to clarify a point for me: If I understand correctly the t test, since it