Re: One tailed vs. Two tailed test

2001-03-15 Thread Jerry Dallal
We don't really disagree. Any apparent disagreement is probably due to the abbreviated kind of discussion that takes place in Usenet. See http://www.tufts.edu/~gdallal/onesided.htm Alan McLean ([EMAIL PROTECTED]) wrote: My point however is still true - that the person who receives the

Re: One tailed vs. Two tailed test

2001-03-15 Thread Alan McLean
I agree that it's the detail about which we disagree! However, one detail is pretty important - I still think you are confusing the trial and the statistical test. The same confusion is shown on the web site. I agree totally that if the treatment appears to be significantly worse than the

Re: One tailed vs. Two tailed test

2001-03-14 Thread RD
On 13 Mar 2001 16:32:15 -0500, [EMAIL PROTECTED] (Herman Rubin) wrote: In article [EMAIL PROTECTED], RD [EMAIL PROTECTED] wrote: On 13 Mar 2001 07:12:33 -0800, [EMAIL PROTECTED] (dennis roberts) wrote: 1. some test statistics are naturally (the way they work anyway) ONE sided with respect to

Re: One tailed vs. Two tailed test

2001-03-14 Thread Herman Rubin
In article [EMAIL PROTECTED], Alan McLean [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote: More importantly, I would say: DON'T DO TESTS. Instead, try to find models that you would be prepared to use to predict the response in as-yet untried circumstances. -- Hypothesis testing is

Re: One tailed vs. Two tailed test

2001-03-14 Thread RD
On 13 Mar 2001 14:23:04 -0800, [EMAIL PROTECTED] (dennis roberts) wrote: well, help me out a bit i give a survey and ... have categorized respondents into male and females ... and also into science major and non science majors ... and find a data table like: MTB chisquare c1 c2 Chi-Square

Re: One tailed vs. Two tailed test

2001-03-13 Thread Alan McLean
Will Hopkins wrote: Responses to various folks. And to everyone touchy about one-tailed tests, let me make it quite clear that I am only promoting them as a way of making a sensible statement about probability. A two-tailed p value has no real meaning, because no real effects are ever

Re: One tailed vs. Two tailed test

2001-03-13 Thread dennis roberts
we have to first separate out 2 things: 1. some test statistics are naturally (the way they work anyway) ONE sided with respect to retain/reject decisions example: chi square test for independence ... we reject ONLY when chi square is LARGER than some CV ... to put a CV at the lower end of

Re: One tailed vs. Two tailed test

2001-03-13 Thread Robert J. MacG. Dawson
dennis roberts wrote: we have to first separate out 2 things: 1. some test statistics are naturally (the way they work anyway) ONE sided with respect to retain/reject decisions example: chi square test for independence ... we reject ONLY when chi square is LARGER than some CV ... to

Re: One tailed vs. Two tailed test

2001-03-13 Thread Herman Rubin
In article p0433010fb6d329af7d2d@[139.80.121.126], Will Hopkins [EMAIL PROTECTED] wrote: At 7:34 PM + 12/3/01, Jerry Dallal wrote: Don't do one-tailed tests. If you are going to do any tests, it makes more sense to one-tailed tests. The resulting p value actually means something that folks

Re: One tailed vs. Two tailed test

2001-03-13 Thread Jerry Dallal
Will Hopkins wrote: At 7:34 PM + 12/3/01, Jerry Dallal wrote: Don't do one-tailed tests. If you are going to do any tests, it makes more sense to one-tailed tests. If you're doing a 1 tailed test, why test at all? Just switch from standard treatment to the new one. Can't do any

Re: One tailed vs. Two tailed test

2001-03-13 Thread RD
On 13 Mar 2001 07:12:33 -0800, [EMAIL PROTECTED] (dennis roberts) wrote: 1. some test statistics are naturally (the way they work anyway) ONE sided with respect to retain/reject decisions example: chi square test for independence ... we reject ONLY when chi square is LARGER than some CV ...

Re: One tailed vs. Two tailed test

2001-03-13 Thread dennis roberts
well, help me out a bit i give a survey and ... have categorized respondents into male and females ... and also into science major and non science majors ... and find a data table like: MTB chisquare c1 c2 Chi-Square Test: C1, C2 Expected counts are printed below observed counts

Re: One tailed vs. Two tailed test

2001-03-13 Thread Herman Rubin
In article [EMAIL PROTECTED], RD [EMAIL PROTECTED] wrote: On 13 Mar 2001 07:12:33 -0800, [EMAIL PROTECTED] (dennis roberts) wrote: 1. some test statistics are naturally (the way they work anyway) ONE sided with respect to retain/reject decisions example: chi square test for independence ...

Re: One tailed vs. Two tailed test

2001-03-13 Thread
In article [EMAIL PROTECTED], RD [EMAIL PROTECTED] writes: On 13 Mar 2001 07:12:33 -0800, [EMAIL PROTECTED] (dennis roberts) wrote: 1. some test statistics are naturally (the way they work anyway) ONE sided with respect to retain/reject decisions example: chi square test for

Re: One tailed vs. Two tailed test

2001-03-13 Thread Will Hopkins
Responses to various folks. And to everyone touchy about one-tailed tests, let me make it quite clear that I am only promoting them as a way of making a sensible statement about probability. A two-tailed p value has no real meaning, because no real effects are ever null. A one-tailed p

One tailed vs. Two tailed test

2001-03-12 Thread auda
Hi, all, We are testing a group of subjects on their performance in two different conditions (say, A and B), and we are testing them individually. We have an alternative hypothesis that reaction time in condition A should be longer than in condition B, so we perform a one-tailed t test. However,

Re: One tailed vs. Two tailed test

2001-03-12 Thread Thom Baguley
auda wrote: Hi, all, We are testing a group of subjects on their performance in two different conditions (say, A and B), and we are testing them individually. We have an alternative hypothesis that reaction time in condition A should be longer than in condition B, so we perform a

Re: One tailed vs. Two tailed test

2001-03-12 Thread Jerry Dallal
auda wrote: Hi, all, We are testing a group of subjects on their performance in two different conditions (say, A and B), and we are testing them individually. We have an alternative hypothesis that reaction time in condition A should be longer than in condition B, so we perform a

Re: One tailed vs. Two tailed test

2001-03-12 Thread Will Hopkins
At 7:34 PM + 12/3/01, Jerry Dallal wrote: Don't do one-tailed tests. If you are going to do any tests, it makes more sense to one-tailed tests. The resulting p value actually means something that folks can understand: it's the probability the true value of the effect is opposite to what

Re: One tailed vs. Two tailed test

2001-03-12 Thread Donald Burrill
On Tue, 13 Mar 2001, Will Hopkins wrote in part: Example: you observe an effect of +5.3 units, one-tailed p = 0.04. Therefore there is a probability of 0.04 that the true value is less than zero. Sorry, that's incorrect. The probability is 0.04 that you would find an effect as large as