
Administrator

[ posted to the SPSSXL mailing list, and to comp.softsys.stat.spss ]
Hello folks. Our university just started using v18. A colleague who was attempting to perform MannWhitney U tests on a couple of variables asked me why SPSS was advising her to "retain the null hypothesis" when the pvalue was well below .05. I said I didn't know, and asked to see the data.
It turns out that there are now socalled "legacy dialogs" under Analyze  Nonparametric. If you fail to notice that, and you use the newfangled dialogs, your analysis is done via NPTESTS rather than NPAR TESTS. The output (the default output, at least) for NPTESTS is VERY sparse  it does not give any descriptive statistics (including the sample sizes), nor does it report the value of the test statistic. It only gives a statement of the null hypothesis, says which test was used, gives a pvalue, and a decision (i.e., reject or retain H0).
IMO, this is a big step in the wrong direction. Does IBM SPSS Statistics really want to market itself by saying things like, "You don't even have to understand statistics to use it!"? The term GIGO comes to mind.
And there's another problem: For one of my colleague's two variables, the "decision" was to retain H0, despite the fact that the pvalue was .013. See below. (And yes, I do know that there are far too many ties here, which is very problematic for rankbased tests. But will the targeted user who "doesn't even have to understand statistics?" know that? I doubt it.)
data list list / Group Y1 Y2 (3f5.0).
begin data
0 0 34
0 0 16
0 0 33
0 0 0
0 0 22
0 0 0
0 46 22
0 0 0
0 0 0
0 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
end data.
variable level Y1 Y2 (scale).
* The default GUI options for Analyze  Nonparametric
* now generate NPTESTS syntax.
*Nonparametric Tests: Independent Samples.
NPTESTS
/INDEPENDENT TEST (Y1 Y2) GROUP (Group)
/MISSING SCOPE=ANALYSIS USERMISSING=EXCLUDE
/CRITERIA ALPHA=0.05 CILEVEL=95.
* Notice that the output is VERY sparse.
* There is no reporting of descriptive stats  not even
* the sample sizes; nor is the test statistic reported.
* A "decision" is reported (reject or retain H0); but
* for variable Y2, the "decision" does not agree with
* the reported pvalue.
* To obtain the oldfashioned NPAR TESTS syntax, one
* must now use the "legacy dialogs" under Analyze  Nonparametric.
NPAR TESTS MW = Y1 Y2 BY group(0,1).


Hi Bruce:
Bruce Weaver wrote:
> [ posted to the SPSSXL mailing list, and to comp.softsys.stat.spss ]
>
> Hello folks. Our university just started using v18. A colleague who was
> attempting to perform MannWhitney U tests on a couple of variables asked
> me why SPSS was advising her to "retain the null hypothesis" when the
> pvalue was well below .05. I said I didn't know, and asked to see the
> data.
>
Given the small sample sizes, you must pay attention to the exact
pvalue (although it will be somewhat biased towards non significance
due to the high number of ties), and it is p=0.063. The asymptotic
approximation is not reliable when both sample sizes are below 20, like
in this case.
Anyway, MannWhitney's U test needs that both sample distributions are
similar in shape and spread. This is clearly not the case with your
data. I would recommend using median test instead:
NPAR TESTS
/MEDIAN=Y1 Y2 BY Group(0 1)
/MISSING ANALYSIS.
The result is significant (using and exact pvalue, BTW).
I DON'T like NPTESTS either. I use a collection of macros that are more
complete (IMHO)
HTH,
Marta GG
> It turns out that there are now socalled "legacy dialogs" under Analyze 
> Nonparametric. If you fail to notice that, and you use the newfangled
> dialogs, your analysis is done via NPTESTS rather than NPAR TESTS. The
> output (the default output, at least) for NPTESTS is VERY sparse  it does
> not give any descriptive statistics (including the sample sizes), nor does
> it report the value of the test statistic. It only gives a statement of the
> null hypothesis, says which test was used, gives a pvalue, and a decision
> (i.e., reject or retain H0).
>
> IMO, this is a big step in the wrong direction. Does IBM SPSS Statistics
> really want to market itself by saying things like, "You don't even have to
> understand statistics to use it!"? The term GIGO comes to mind.
>
> And there's another problem: For one of my colleague's two variables, the
> "decision" was to retain H0, despite the fact that the pvalue was .013.
> See below. (And yes, I do know that there are far too many ties here, which
> is very problematic for rankbased tests. But will the targeted user who
> "doesn't even have to understand statistics?" know that? I doubt it.)
>
> data list list / Group Y1 Y2 (3f5.0).
> begin data
> 0 0 34
> 0 0 16
> 0 0 33
> 0 0 0
> 0 0 22
> 0 0 0
> 0 46 22
> 0 0 0
> 0 0 0
> 0 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> end data.
>
> variable level Y1 Y2 (scale).
>
> * The default GUI options for Analyze  Nonparametric
> * now generate NPTESTS syntax.
>
> *Nonparametric Tests: Independent Samples.
> NPTESTS
> /INDEPENDENT TEST (Y1 Y2) GROUP (Group)
> /MISSING SCOPE=ANALYSIS USERMISSING=EXCLUDE
> /CRITERIA ALPHA=0.05 CILEVEL=95.
>
> * Notice that the output is VERY sparse.
> * There is no reporting of descriptive stats  not even
> * the sample sizes; nor is the test statistic reported.
> * A "decision" is reported (reject or retain H0); but
> * for variable Y2, the "decision" does not agree with
> * the reported pvalue.
>
> * To obtain the oldfashioned NPAR TESTS syntax, one
> * must now use the "legacy dialogs" under Analyze  Nonparametric.
>
> NPAR TESTS MW = Y1 Y2 BY group(0,1).
>
>
>
> 
> 
> Bruce Weaver
> [hidden email]
> http://sites.google.com/a/lakeheadu.ca/bweaver/>
> "When all else fails, RTFM."
>
> NOTE: My Hotmail account is not monitored regularly.
> To send me an email, please use the address shown above.
>
> 
> View this message in context: http://spssxdiscussion.1045642.n5.nabble.com/RANTNPTESTSvsNPARTESTStp2807847p2807847.html> Sent from the SPSSX Discussion mailing list archive at Nabble.com.
>
> =====================
> To manage your subscription to SPSSXL, send a message to
> [hidden email] (not to SPSSXL), with no body text except the
> command. To leave the list, send the command
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>
>

For miscellaneous SPSS related statistical stuff, visit:
http://gjyp.nl/marta/=====================
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Re: RANT: NPTESTS vs NPAR TESTS
I recommend the legacy dialogues for n onparameteric to all my friends ans students
The new part is complicated to use for INPUT and seriously lacking for OUTPUT
Yet another example of PASW letting their designers drive the interface
Typically they have no idea about statistics [as eg shows] and no idea about hci as evidenced by lack of user testing
Best
Diana
On 08/09/2010 14:44, "Marta GarcíaGranero" <mgarciagranero@...> wrote:
Hi Bruce:
Bruce Weaver wrote:
> [ posted to the SPSSXL mailing list, and to comp.softsys.stat.spss ]
>
> Hello folks. Our university just started using v18. A colleague who was
> attempting to perform MannWhitney U tests on a couple of variables asked
> me why SPSS was advising her to "retain the null hypothesis" when the
> pvalue was well below .05. I said I didn't know, and asked to see the
> data.
>
Given the small sample sizes, you must pay attention to the exact
pvalue (although it will be somewhat biased towards non significance
due to the high number of ties), and it is p=0.063. The asymptotic
approximation is not reliable when both sample sizes are below 20, like
in this case.
Anyway, MannWhitney's U test needs that both sample distributions are
similar in shape and spread. This is clearly not the case with your
data. I would recommend using median test instead:
NPAR TESTS
/MEDIAN=Y1 Y2 BY Group(0 1)
/MISSING ANALYSIS.
The result is significant (using and exact pvalue, BTW).
I DON'T like NPTESTS either. I use a collection of macros that are more
complete (IMHO)
HTH,
Marta GG
> It turns out that there are now socalled "legacy dialogs" under Analyze 
> Nonparametric. If you fail to notice that, and you use the newfangled
> dialogs, your analysis is done via NPTESTS rather than NPAR TESTS. The
> output (the default output, at least) for NPTESTS is VERY sparse  it does
> not give any descriptive statistics (including the sample sizes), nor does
> it report the value of the test statistic. It only gives a statement of the
> null hypothesis, says which test was used, gives a pvalue, and a decision
> (i.e., reject or retain H0).
>
> IMO, this is a big step in the wrong direction. Does IBM SPSS Statistics
> really want to market itself by saying things like, "You don't even have to
> understand statistics to use it!"? The term GIGO comes to mind.
>
> And there's another problem: For one of my colleague's two variables, the
> "decision" was to retain H0, despite the fact that the pvalue was .013.
> See below. (And yes, I do know that there are far too many ties here, which
> is very problematic for rankbased tests. But will the targeted user who
> "doesn't even have to understand statistics?" know that? I doubt it.)
>
> data list list / Group Y1 Y2 (3f5.0).
> begin data
> 0 0 34
> 0 0 16
> 0 0 33
> 0 0 0
> 0 0 22
> 0 0 0
> 0 46 22
> 0 0 0
> 0 0 0
> 0 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> end data.
>
> variable level Y1 Y2 (scale).
>
> * The default GUI options for Analyze  Nonparametric
> * now generate NPTESTS syntax.
>
> *Nonparametric Tests: Independent Samples.
> NPTESTS
> /INDEPENDENT TEST (Y1 Y2) GROUP (Group)
> /MISSING SCOPE=ANALYSIS USERMISSING=EXCLUDE
> /CRITERIA ALPHA=0.05 CILEVEL=95.
>
> * Notice that the output is VERY sparse.
> * There is no reporting of descriptive stats  not even
> * the sample sizes; nor is the test statistic reported.
> * A "decision" is reported (reject or retain H0); but
> * for variable Y2, the "decision" does not agree with
> * the reported pvalue.
>
> * To obtain the oldfashioned NPAR TESTS syntax, one
> * must now use the "legacy dialogs" under Analyze  Nonparametric.
>
> NPAR TESTS MW = Y1 Y2 BY group(0,1).
>
>
>
> 
> 
> Bruce Weaver
> bweaver@...
> http://sites.google.com/a/lakeheadu.ca/bweaver/
>
> "When all else fails, RTFM."
>
> NOTE: My Hotmail account is not monitored regularly.
> To send me an email, please use the address shown above.
>
> 
> View this message in context: http://spssxdiscussion.1045642.n5.nabble.com/RANTNPTESTSvsNPARTESTStp2807847p2807847.html
> Sent from the SPSSX Discussion mailing list archive at Nabble.com.
>
> =====================
> To manage your subscription to SPSSXL, send a message to
> LISTSERV@... (not to SPSSXL), with no body text except the
> command. To leave the list, send the command
> SIGNOFF SPSSXL
> For a list of commands to manage subscriptions, send the command
> INFO REFCARD
>
>

For miscellaneous SPSS related statistical stuff, visit:
http://gjyp.nl/marta/
=====================
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Professor Diana Kornbrot
email: d.e.kornbrot@...
web: http://web.me.com/kornbrot/KornbrotHome.html
Work
Centre for Lifespan & Chronic Illness Research, CLiCIR
School of Psychology
University of Hertfordshire
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mobile: +44 (0) 7403 18 16 12
fax: +44 (0) 8707 06 49 97


Hi Bruce,
With regard to the disagreement between
the significance displayed in the initial output table and the decision
recommended, there's a bug, as described in the resolution included below.
David Nichols
Statistical Support
SPSS, an IBM Company
Resolution #90896
Problem Summary:
NPTESTS MannWhitney test output significance and decision don't agree
Problem Description:
I'm running a MannWhitney test in the NPTESTS procedure in IBM SPSS Statistics.
In the resulting output, I sometimes see a p value below my specified critical
level in the Sig. column, along with Retain the null hypothesis in the
Decision column, or vice versa. Why is this happening?
Resolution Summary:
This problem has been reported to SPSS Development  it occurs because
significance is based on asymptotic results, decision on exact results
Resolution Description:
If the sample size is sufficiently small, you get both asymptotic and exact
results for the MannWhitney test. The results shown in the main initial
output in the Viewer should be consistent in using the exact significance
levels, but are currently using significance levels from the asymptotic
test and basing the decision on the exact test. The problem has been reported
to SPSS Development and will be fixed in a future release. In the meantime,
you can doubleclick on the output to activate the Viewer and look at the
results in the righthand screen for the variable(s) of interest and see
both asymptotic and exact significance levels. We apologize for any resulting
inconvenience.
[ posted to the SPSSXL mailing list, and to comp.softsys.stat.spss
]
Hello folks. Our university just started using v18. A colleague
who was
attempting to perform MannWhitney U tests on a couple of variables
asked
me why SPSS was advising her to "retain the null hypothesis"
when the
pvalue was well below .05. I said I didn't know, and asked to see
the
data.
It turns out that there are now socalled "legacy dialogs" under
Analyze 
Nonparametric. If you fail to notice that, and you use the newfangled
dialogs, your analysis is done via NPTESTS rather than NPAR TESTS. The
output (the default output, at least) for NPTESTS is VERY sparse  it
does
not give any descriptive statistics (including the sample sizes), nor does
it report the value of the test statistic. It only gives a statement
of the
null hypothesis, says which test was used, gives a pvalue, and a decision
(i.e., reject or retain H0).
IMO, this is a big step in the wrong direction. Does IBM SPSS Statistics
really want to market itself by saying things like, "You don't even
have to
understand statistics to use it!"? The term GIGO comes to mind.
And there's another problem: For one of my colleague's two variables,
the
"decision" was to retain H0, despite the fact that the
pvalue was .013.
See below. (And yes, I do know that there are far too many ties here,
which
is very problematic for rankbased tests. But will the targeted user
who
"doesn't even have to understand statistics?" know that? I
doubt it.)
data list list / Group Y1 Y2 (3f5.0).
begin data
0 0 34
0 0 16
0 0 33
0 0 0
0 0 22
0 0 0
0 46 22
0 0 0
0 0 0
0 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
end data.
variable level Y1 Y2 (scale).
* The default GUI options for Analyze  Nonparametric
* now generate NPTESTS syntax.
*Nonparametric Tests: Independent Samples.
NPTESTS
/INDEPENDENT TEST (Y1 Y2) GROUP (Group)
/MISSING SCOPE=ANALYSIS USERMISSING=EXCLUDE
/CRITERIA ALPHA=0.05 CILEVEL=95.
* Notice that the output is VERY sparse.
* There is no reporting of descriptive stats  not even
* the sample sizes; nor is the test statistic reported.
* A "decision" is reported (reject or retain H0); but
* for variable Y2, the "decision" does not agree with
* the reported pvalue.
* To obtain the oldfashioned NPAR TESTS syntax, one
* must now use the "legacy dialogs" under Analyze  Nonparametric.
NPAR TESTS MW = Y1 Y2 BY group(0,1).


Bruce Weaver
[hidden email]
http://sites.google.com/a/lakeheadu.ca/bweaver/
"When all else fails, RTFM."
NOTE: My Hotmail account is not monitored regularly.
To send me an email, please use the address shown above.

View this message in context: http://spssxdiscussion.1045642.n5.nabble.com/RANTNPTESTSvsNPARTESTStp2807847p2807847.html
Sent from the SPSSX Discussion mailing list archive at Nabble.com.
=====================
To manage your subscription to SPSSXL, send a message to
[hidden email] (not to SPSSXL), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSXL
For a list of commands to manage subscriptions, send the command
INFO REFCARD

Administrator

Thanks David. I didn't know about the "model viewer" that pops up when you doubleclick on the output. The output shown there is actually quite nice  I like the plot showing the distributions for the two groups, for example. If this had appeared as part of the standard output, I would have avoided a rant. ;)
Cheers,
Bruce
SPSS Support2 wrote
Hi Bruce,
With regard to the disagreement between the significance displayed in the
initial output table and the decision recommended, there's a bug, as
described in the resolution included below.
David Nichols
Statistical Support
SPSS, an IBM Company
Resolution #90896
Problem Summary:
NPTESTS MannWhitney test output significance and decision don't agree
Problem Description:
I'm running a MannWhitney test in the NPTESTS procedure in IBM SPSS
Statistics. In the resulting output, I sometimes see a p value below my
specified critical level in the Sig. column, along with Retain the null
hypothesis in the Decision column, or vice versa. Why is this happening?
Resolution Summary:
This problem has been reported to SPSS Development  it occurs because
significance is based on asymptotic results, decision on exact results
Resolution Description:
If the sample size is sufficiently small, you get both asymptotic and
exact results for the MannWhitney test. The results shown in the main
initial output in the Viewer should be consistent in using the exact
significance levels, but are currently using significance levels from the
asymptotic test and basing the decision on the exact test. The problem has
been reported to SPSS Development and will be fixed in a future release.
In the meantime, you can doubleclick on the output to activate the Viewer
and look at the results in the righthand screen for the variable(s) of
interest and see both asymptotic and exact significance levels. We
apologize for any resulting inconvenience.
From:
Bruce Weaver <bruce.weaver@hotmail.com> To:
SPSSXL@LISTSERV.UGA.EDU
Date:
09/08/2010 08:12 AM
Subject:
RANT: NPTESTS vs NPAR TESTS
Sent by:
"SPSSX(r) Discussion" <SPSSXL@LISTSERV.UGA.EDU> [ posted to the SPSSXL mailing list, and to comp.softsys.stat.spss ]
Hello folks. Our university just started using v18. A colleague who was
attempting to perform MannWhitney U tests on a couple of variables asked
me why SPSS was advising her to "retain the null hypothesis" when the
pvalue was well below .05. I said I didn't know, and asked to see the
data.
It turns out that there are now socalled "legacy dialogs" under Analyze 
Nonparametric. If you fail to notice that, and you use the newfangled
dialogs, your analysis is done via NPTESTS rather than NPAR TESTS. The
output (the default output, at least) for NPTESTS is VERY sparse  it
does
not give any descriptive statistics (including the sample sizes), nor does
it report the value of the test statistic. It only gives a statement of
the
null hypothesis, says which test was used, gives a pvalue, and a decision
(i.e., reject or retain H0).
IMO, this is a big step in the wrong direction. Does IBM SPSS Statistics
really want to market itself by saying things like, "You don't even have
to
understand statistics to use it!"? The term GIGO comes to mind.
And there's another problem: For one of my colleague's two variables, the
"decision" was to retain H0, despite the fact that the pvalue was .013.
See below. (And yes, I do know that there are far too many ties here,
which
is very problematic for rankbased tests. But will the targeted user who
"doesn't even have to understand statistics?" know that? I doubt it.)
data list list / Group Y1 Y2 (3f5.0).
begin data
0 0 34
0 0 16
0 0 33
0 0 0
0 0 22
0 0 0
0 46 22
0 0 0
0 0 0
0 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
1 0 0
end data.
variable level Y1 Y2 (scale).
* The default GUI options for Analyze  Nonparametric
* now generate NPTESTS syntax.
*Nonparametric Tests: Independent Samples.
NPTESTS
/INDEPENDENT TEST (Y1 Y2) GROUP (Group)
/MISSING SCOPE=ANALYSIS USERMISSING=EXCLUDE
/CRITERIA ALPHA=0.05 CILEVEL=95.
* Notice that the output is VERY sparse.
* There is no reporting of descriptive stats  not even
* the sample sizes; nor is the test statistic reported.
* A "decision" is reported (reject or retain H0); but
* for variable Y2, the "decision" does not agree with
* the reported pvalue.
* To obtain the oldfashioned NPAR TESTS syntax, one
* must now use the "legacy dialogs" under Analyze  Nonparametric.
NPAR TESTS MW = Y1 Y2 BY group(0,1).


Bruce Weaver
bweaver@lakeheadu.ca
http://sites.google.com/a/lakeheadu.ca/bweaver/"When all else fails, RTFM."
NOTE: My Hotmail account is not monitored regularly.
To send me an email, please use the address shown above.

View this message in context:
http://spssxdiscussion.1045642.n5.nabble.com/RANTNPTESTSvsNPARTESTStp2807847p2807847.htmlSent from the SPSSX Discussion mailing list archive at Nabble.com.
=====================
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LISTSERV@LISTSERV.UGA.EDU (not to SPSSXL), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSXL
For a list of commands to manage subscriptions, send the command
INFO REFCARD


Thank you! I've retired!
Necia A. Black, Ph.D. email: [hidden email]
246 Computing Center Web URL: http://www.acsu.buffalo.edu/~blackSUNYBuffalo
Buffalo, New York 14260
=====================
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Administrator

In reply to this post by Marta GarciaGranero
Hi Marta. As it happens, I ended up at the same place you did. I suggested converting things to 2x2 tables, with Group in the rows, and None vs Some in the columns. Given that the grand median = 0 in both cases, my 2x2 tables are exactly the same as those used for the median test. One difference is that I recommended using the N1 chisquare in the case where all expected counts were large enough.
http://www.iancampbell.co.uk/twobytwo/calculator.htmCheers,
Bruce
Marta GarcíaGranero2 wrote
Hi Bruce:
Bruce Weaver wrote:
> [ posted to the SPSSXL mailing list, and to comp.softsys.stat.spss ]
>
> Hello folks. Our university just started using v18. A colleague who was
> attempting to perform MannWhitney U tests on a couple of variables asked
> me why SPSS was advising her to "retain the null hypothesis" when the
> pvalue was well below .05. I said I didn't know, and asked to see the
> data.
>
Given the small sample sizes, you must pay attention to the exact
pvalue (although it will be somewhat biased towards non significance
due to the high number of ties), and it is p=0.063. The asymptotic
approximation is not reliable when both sample sizes are below 20, like
in this case.
Anyway, MannWhitney's U test needs that both sample distributions are
similar in shape and spread. This is clearly not the case with your
data. I would recommend using median test instead:
NPAR TESTS
/MEDIAN=Y1 Y2 BY Group(0 1)
/MISSING ANALYSIS.
The result is significant (using and exact pvalue, BTW).
I DON'T like NPTESTS either. I use a collection of macros that are more
complete (IMHO)
HTH,
Marta GG
> It turns out that there are now socalled "legacy dialogs" under Analyze 
> Nonparametric. If you fail to notice that, and you use the newfangled
> dialogs, your analysis is done via NPTESTS rather than NPAR TESTS. The
> output (the default output, at least) for NPTESTS is VERY sparse  it does
> not give any descriptive statistics (including the sample sizes), nor does
> it report the value of the test statistic. It only gives a statement of the
> null hypothesis, says which test was used, gives a pvalue, and a decision
> (i.e., reject or retain H0).
>
> IMO, this is a big step in the wrong direction. Does IBM SPSS Statistics
> really want to market itself by saying things like, "You don't even have to
> understand statistics to use it!"? The term GIGO comes to mind.
>
> And there's another problem: For one of my colleague's two variables, the
> "decision" was to retain H0, despite the fact that the pvalue was .013.
> See below. (And yes, I do know that there are far too many ties here, which
> is very problematic for rankbased tests. But will the targeted user who
> "doesn't even have to understand statistics?" know that? I doubt it.)
>
> data list list / Group Y1 Y2 (3f5.0).
> begin data
> 0 0 34
> 0 0 16
> 0 0 33
> 0 0 0
> 0 0 22
> 0 0 0
> 0 46 22
> 0 0 0
> 0 0 0
> 0 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> 1 0 0
> end data.
>
> variable level Y1 Y2 (scale).
>
> * The default GUI options for Analyze  Nonparametric
> * now generate NPTESTS syntax.
>
> *Nonparametric Tests: Independent Samples.
> NPTESTS
> /INDEPENDENT TEST (Y1 Y2) GROUP (Group)
> /MISSING SCOPE=ANALYSIS USERMISSING=EXCLUDE
> /CRITERIA ALPHA=0.05 CILEVEL=95.
>
> * Notice that the output is VERY sparse.
> * There is no reporting of descriptive stats  not even
> * the sample sizes; nor is the test statistic reported.
> * A "decision" is reported (reject or retain H0); but
> * for variable Y2, the "decision" does not agree with
> * the reported pvalue.
>
> * To obtain the oldfashioned NPAR TESTS syntax, one
> * must now use the "legacy dialogs" under Analyze  Nonparametric.
>
> NPAR TESTS MW = Y1 Y2 BY group(0,1).
>
>
>
> 
> 
> Bruce Weaver
> bweaver@lakeheadu.ca
> http://sites.google.com/a/lakeheadu.ca/bweaver/>
> "When all else fails, RTFM."
>
> NOTE: My Hotmail account is not monitored regularly.
> To send me an email, please use the address shown above.
>
> 
> View this message in context: http://spssxdiscussion.1045642.n5.nabble.com/RANTNPTESTSvsNPARTESTStp2807847p2807847.html> Sent from the SPSSX Discussion mailing list archive at Nabble.com.
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For miscellaneous SPSS related statistical stuff, visit:
http://gjyp.nl/marta/=====================
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There's another minor angle on that new command which is that all the model
graphics, which look very nice, do not directly print. They print but only
after you have double clicked on result box and then select print on the
right hand pane. I'm not interested in ranting on this (and I won't say
anything more on this) but I vote against hidden output. I prefer everything
to be visable in the output file, whether viewed on a screen or on paper.
Gene Maguin
Original Message
From: SPSSX(r) Discussion [mailto: [hidden email]] On Behalf Of
Bruce Weaver
Sent: Wednesday, September 08, 2010 3:50 PM
To: [hidden email]
Subject: Re: RANT: NPTESTS vs NPAR TESTS
Hi Marta. As it happens, I ended up at the same place you did. I suggested
converting things to 2x2 tables, with Group in the rows, and None vs Some in
the columns. Given that the grand median = 0 in both cases, my 2x2 tables
are exactly the same as those used for the median test. One difference is
that I recommended using the N1 chisquare in the case where all expected
counts were large enough.
http://www.iancampbell.co.uk/twobytwo/calculator.htmCheers,
Bruce
Marta GarcíaGranero2 wrote:
>
> Hi Bruce:
>
> Bruce Weaver wrote:
>> [ posted to the SPSSXL mailing list, and to comp.softsys.stat.spss ]
>>
>> Hello folks. Our university just started using v18. A colleague who was
>> attempting to perform MannWhitney U tests on a couple of variables
>> asked
>> me why SPSS was advising her to "retain the null hypothesis" when the
>> pvalue was well below .05. I said I didn't know, and asked to see the
>> data.
>>
>
> Given the small sample sizes, you must pay attention to the exact
> pvalue (although it will be somewhat biased towards non significance
> due to the high number of ties), and it is p=0.063. The asymptotic
> approximation is not reliable when both sample sizes are below 20, like
> in this case.
>
> Anyway, MannWhitney's U test needs that both sample distributions are
> similar in shape and spread. This is clearly not the case with your
> data. I would recommend using median test instead:
>
> NPAR TESTS
> /MEDIAN=Y1 Y2 BY Group(0 1)
> /MISSING ANALYSIS.
>
>
> The result is significant (using and exact pvalue, BTW).
>
> I DON'T like NPTESTS either. I use a collection of macros that are more
> complete (IMHO)
>
> HTH,
> Marta GG
>> It turns out that there are now socalled "legacy dialogs" under Analyze
>> 
>> Nonparametric. If you fail to notice that, and you use the newfangled
>> dialogs, your analysis is done via NPTESTS rather than NPAR TESTS. The
>> output (the default output, at least) for NPTESTS is VERY sparse  it
>> does
>> not give any descriptive statistics (including the sample sizes), nor
>> does
>> it report the value of the test statistic. It only gives a statement of
>> the
>> null hypothesis, says which test was used, gives a pvalue, and a
>> decision
>> (i.e., reject or retain H0).
>>
>> IMO, this is a big step in the wrong direction. Does IBM SPSS Statistics
>> really want to market itself by saying things like, "You don't even have
>> to
>> understand statistics to use it!"? The term GIGO comes to mind.
>>
>> And there's another problem: For one of my colleague's two variables,
>> the
>> "decision" was to retain H0, despite the fact that the pvalue was .013.
>> See below. (And yes, I do know that there are far too many ties here,
>> which
>> is very problematic for rankbased tests. But will the targeted user who
>> "doesn't even have to understand statistics?" know that? I doubt it.)
>>
>> data list list / Group Y1 Y2 (3f5.0).
>> begin data
>> 0 0 34
>> 0 0 16
>> 0 0 33
>> 0 0 0
>> 0 0 22
>> 0 0 0
>> 0 46 22
>> 0 0 0
>> 0 0 0
>> 0 0 0
>> 1 0 0
>> 1 0 0
>> 1 0 0
>> 1 0 0
>> 1 0 0
>> 1 0 0
>> 1 0 0
>> 1 0 0
>> 1 0 0
>> 1 0 0
>> end data.
>>
>> variable level Y1 Y2 (scale).
>>
>> * The default GUI options for Analyze  Nonparametric
>> * now generate NPTESTS syntax.
>>
>> *Nonparametric Tests: Independent Samples.
>> NPTESTS
>> /INDEPENDENT TEST (Y1 Y2) GROUP (Group)
>> /MISSING SCOPE=ANALYSIS USERMISSING=EXCLUDE
>> /CRITERIA ALPHA=0.05 CILEVEL=95.
>>
>> * Notice that the output is VERY sparse.
>> * There is no reporting of descriptive stats  not even
>> * the sample sizes; nor is the test statistic reported.
>> * A "decision" is reported (reject or retain H0); but
>> * for variable Y2, the "decision" does not agree with
>> * the reported pvalue.
>>
>> * To obtain the oldfashioned NPAR TESTS syntax, one
>> * must now use the "legacy dialogs" under Analyze  Nonparametric.
>>
>> NPAR TESTS MW = Y1 Y2 BY group(0,1).
>>
>>
>>
>> 
>> 
>> Bruce Weaver
>> [hidden email]
>> http://sites.google.com/a/lakeheadu.ca/bweaver/>>
>> "When all else fails, RTFM."
>>
>> NOTE: My Hotmail account is not monitored regularly.
>> To send me an email, please use the address shown above.
>>
>> 
>> View this message in context:
>>
http://spssxdiscussion.1045642.n5.nabble.com/RANTNPTESTSvsNPARTESTStp2807847p2807847.html
>> Sent from the SPSSX Discussion mailing list archive at Nabble.com.
>>
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>>
>
>
> 
> For miscellaneous SPSS related statistical stuff, visit:
> http://gjyp.nl/marta/>
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Bruce Weaver
[hidden email]
http://sites.google.com/a/lakeheadu.ca/bweaver/"When all else fails, RTFM."
NOTE: My Hotmail account is not monitored regularly.
To send me an email, please use the address shown above.

View this message in context:
http://spssxdiscussion.1045642.n5.nabble.com/RANTNPTESTSvsNPARTESTStp2807847p2810189.html
Sent from the SPSSX Discussion mailing list archive at Nabble.com.
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Administrator

On Wed, 8 Sep 2010 15:35:26 0400, necia < [hidden email]> wrote:
>Thank you! I've retired!
>
>Necia A. Black, Ph.D. email: [hidden email]
>246 Computing Center Web URL: http://www.acsu.buffalo.edu/~black>SUNYBuffalo
>Buffalo, New York 14260
>
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Congratulations Necia!!
I don't know if you would remember me, but we used to chat on the phone
on occasion something like 20 years ago when I did TekSport for SPSS!!!
You always had challenging questions! I am sure your students will miss
your support!
Best regards, David
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Ed Tesiny
[hidden email]
Original Message
From: SPSSX(r) Discussion [mailto: [hidden email]] On Behalf Of
David Marso
Sent: Friday, September 10, 2010 7:18 AM
To: [hidden email]
Subject: Re: Please remove me from SPSSXL
On Wed, 8 Sep 2010 15:35:26 0400, necia < [hidden email]> wrote:
>Thank you! I've retired!
>
>Necia A. Black, Ph.D. email: [hidden email]
>246 Computing Center Web
URL: http://www.acsu.buffalo.edu/~black>SUNYBuffalo
>Buffalo, New York 14260
>
>=====================
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Congratulations Necia!!
I don't know if you would remember me, but we used to chat on the phone
on occasion something like 20 years ago when I did TekSport for SPSS!!!
You always had challenging questions! I am sure your students will miss
your support!
Best regards, David
=====================
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David Marso wrote
Congratulations Necia!!
I don't know if you would remember me...
.oO(Let me think about that...is David a forgettable type? Hmmm. Somehow, I doubt it.)

