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 necessary theoretical 'scaffolding' or 'superceded procedures', and what one 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

Re: Student's t vs. z tests

2001-04-24 Thread Jerry Dallal
dennis roberts wrote: > start with the realistic case ... even if it takes a bit more "doing" to > explain it Depends what you're trying to teach. If mathematical statistics, I wouldn't think of starting with a t. If data analysis, I wouldn't think of starting with a z. As a read through some

Re: Student's t vs. z tests

2001-04-23 Thread Radford Neal
In article <[EMAIL PROTECTED]>, dennis roberts <[EMAIL PROTECTED]> wrote: >this is why i personally don't like to start with the case where you assume >that you know sigma ... as a "simplification" ... since it is totally >unrealistic > >start with the realistic case ... even if it takes a bit

Re: Student's t vs. z tests

2001-04-22 Thread RCKnodt
Dennis How many actual times do you meet with the class during the course of one term? I know that when I taught we had the undergraduate students meet for 1-1/2 hours for from 21 to 30 sessions depending on the department. In graduate school we met with the students for 2 hours per class fo

Re: Student's t vs. z tests

2001-04-22 Thread dennis roberts
At 05:15 PM 4/22/01 -0400, Rich Ulrich wrote: >On 21 Apr 2001 13:04:55 -0700, [EMAIL PROTECTED] (Will Hopkins) >wrote: > >So you guys are all giving advice about teaching statistics to >psychology majors/ graduates, who have no aspirations or >potential for being anything more than "consumers" (re

Re: Student's t vs. z tests

2001-04-22 Thread Rich Ulrich
On 21 Apr 2001 13:04:55 -0700, [EMAIL PROTECTED] (Will Hopkins) wrote: > I've joined this one at the fag end. I'm with Dennis Roberts. The way I > would put it is this: the PRINCIPLE of a sampling distribution is actually > incredibly simple: keep repeating the study and this is the sort of

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

Re: Student's t vs. z tests

2001-04-21 Thread Will Hopkins
I've joined this one at the fag end. I'm with Dennis Roberts. The way I would put it is this: the PRINCIPLE of a sampling distribution is actually incredibly simple: keep repeating the study and this is the sort of spread you get for the statistic you're interested in. What makes it incredi

Re: Student's t vs. z tests

2001-04-20 Thread dennis roberts
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 obtain the probabilities? good question but, NO

Re: Student's t vs. z tests

2001-04-20 Thread Christopher J. Mecklin
Jim, Dennis, list at large I like Jim's rationale for introducing the binomial first rather than the normal or t. I may try it next semester (too late this semester). He much more eloquently explained why we may not wish to jump straight to the t-test than I did. Chris At 10:58 AM 04/20/200

Re: Student's t vs. z tests

2001-04-20 Thread jim clark
Hi It has been a few years since teaching intro stats to psych students, but I too liked the sequence: binomial -> normal -> t-distribution ... The binomial allows students with basic probability skills to actually calculate the probabilities for a sampling distribution. This provides a solid

Re: Student's t vs. z tests

2001-04-20 Thread Jon Cryer
I don't believe anyone has bothered to define what they mean by a z-test. There are two issues that must be dealt with: (1), What statistic is to be used and (2), what distribution is to be used to assess the size of that statistic. I contend that a z "statistic," viz., (Ybar-mu0)/(sigma/sqrt(n))

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,

Re: Student's t vs. z tests

2001-04-20 Thread Mike Granaas
On Fri, 20 Apr 2001, dennis roberts wrote: > > what i would like to see .. which is probably impossible in general (and > has been discussed before) ... it a more integrated approach to data > collection ... WITHIN THE SAME COURSE OR A SEQUENCE OF COURSES ... so that > when you get to the ana

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 de

Re: Student's t vs. z tests

2001-04-20 Thread Robert J. MacG. Dawson
I wrote, suggesting that forthose with a little learning the Z test is a dangerous thing, and Rich Ulrich responded: > Mainly, I disagree. > > I had read 3 or 4 statistic books and used several stat programs > before I enrolled in graduate courses. One of the *big surprises* to > me was to l

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 wor

Re: Student's t vs. z tests

2001-04-19 Thread dennis roberts
At 08:46 AM 4/20/01 +1000, Alan McLean wrote: >So the two good reasons are - that the z test is the basis for the t, >and the understanding that knowledge has a very direct value. > >I hasten to add that 'knowledge' here is always understood to be >'assumed knowledge' - as it always is in statist

Re: Student's t vs. z tests

2001-04-19 Thread Alan McLean
There is at least two very good pedagogical reasons for teaching z tests. Both the z and t tests are based on normality - the t test is used only because the model standard deviation is unknown or rather, there is no assumed value for it. Whether or not this is in practice 'always' the case is irr

Re: Student's t vs. z tests

2001-04-19 Thread Rich Ulrich
On 19 Apr 2001 05:26:25 -0700, [EMAIL PROTECTED] (Robert J. MacG. Dawson) wrote: [ ... ] > The z test and interval do have some value as a pedagogical > scaffold with the better students who are intended to actually > _understand_ the t test at a mathematical level by the end of the > c

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 studen

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. Mec

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 under

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 ... th

Re: Student's t vs. z tests

2001-04-19 Thread Christopher J. Mecklin
As a reply to Dennis' comments: I wage the same fight in my head each semester about this time, when I'm introducing hypo. testing to students in my undergrad intro to stats class. I teach out of Moore and McCabe. It seems to me that a possible justification for introducing CIs and hypothesi

Re: Student's t vs. z tests

2001-04-19 Thread dennis roberts
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 first thing observant students will ask when you say to them ... assume SR

Re: Student's t vs. z tests

2001-04-18 Thread David J Firth
: You're running into a historical artifact: in pre-computer days, using the : normal distribution rather than the t distribution reduced the size of the : tables you had to work with. Nowadays, a computer can compute a t : probability just as easily as a z probability, so unless you're in the

RE: Student's t vs. z tests

2001-04-17 Thread Mark W. Humphries
vant ones. Cheers, Mark -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Eric Bohlman Sent: Tuesday, April 17, 2001 4:44 AM To: [EMAIL PROTECTED] Subject: Re: Student's t vs. z tests Mark W. Humphries <[EMAIL PROTECTED]> wrote: > Hi, > I am a

Re: Student's t vs. z tests

2001-04-17 Thread Joe Ward
Sent: Monday, April 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

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

2001-04-16 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, sinc

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 t