From rbaer at atsu.edu  Wed Oct 27 16:25:34 2004
From: rbaer at atsu.edu (rbaer@atsu.edu)
Date: Wed Oct 27 16:25:39 2004
Subject: [Rd] wish - cor.test output order change (PR#7315)
Message-ID: <20041027142534.711BB11363@slim.kubism.ku.dk>

Full_Name: Rob Baer
Version: 2.0.0
OS: Windows
Submission from: (NULL) (198.209.172.106)


Request/wish summary: state the alternative hypothesis before the t-test and
p-value

A typical cor.test output looks like the following:
> x=runif(30)*10
> y=runif(30)*10
> cor.test(x,y)

        Pearson's product-moment correlation

data:  x and y 
t = 0.6161, df = 28, p-value = 0.5428
alternative hypothesis: true correlation is not equal to 0 
95 percent confidence interval:
 -0.2552588  0.4568795 
sample estimates:
      cor 
0.1156454 
--------------------------------------------------------------
Rationale
I have the recurring problem of students misinterpreting the alternative
hypothesis statement as an interpretation of the t-test p-value not as a "tail
decision".  The "quick students" think R has made a mistake.  The "slow
students" (please save me) accept the alternative hypothesis with huge p-values
"because the program told them to".  All students seem confused. If this had
affected a single group of students, I'd let it go, but this is a recurring
theme with each new crop.

Proposed fix.  Generaly, we decide on an alternative hypothesis (or should) as
an a priori statement. I think that there would be MUCH LESS confusing if the
printed hypothesis statement came BEFORE the t-test and p-value output.  This
should put it in conceptual sequence; it would not be so easily confused with an
interpretation.  

This same problem happens in some other test output as well.  For these, a
similar order change could greatly reduce confusion about what is being stated. 
If the output code is shared, the fix would only have to be done once.

Thanks for considering it.


[Rd] wish - cor.test output order change (PR#7315)
rbaer@atsu.edu