split-half reliability

[AR-4]

Dear list:

    When testing for split-half reliability is it a good number a
Spearman-Brown Coefficient of 0.88?
n=1300. and I have 16 items in my questionnaire.

Thank you in advance.

[statisticsdoc]

www.statisticsdoc.com
Stephen Brand

Dear AR,

This is a very good number for split-half reliability.  I am assuming that
none of the items are redundant (i.e., simply paraphrase each other).

Best,

Stephen Brand


For personalized and professional consultation in statistics and research
design, visit
www.statisticsdoc.com


-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]]On Behalf Of
AR
Sent: Monday, December 04, 2006 5:08 AM
To: [hidden email]
Subject: split-half reliability


Dear list:

    When testing for split-half reliability is it a good number a
Spearman-Brown Coefficient of 0.88?
n=1300. and I have 16 items in my questionnaire.

Thank you in advance.

[Art Kendall]

Split half-reliability was done in the days of hand computation to
estimate internal consistency.

It is pretty much a historical artifact.   It is twenty or twenty-five
years since I have seen it actually used.

Since you are posting on The SPSS list, I suggest you use Cronbach's
alpha from the RELIABILITY procedure.

Art Kendall
Social Research Consultants

AR wrote:

> Dear list:
>
>    When testing for split-half reliability is it a good number a
> Spearman-Brown Coefficient of 0.88?
> n=1300. and I have 16 items in my questionnaire.
>
> Thank you in advance.
>
>

[Jamie Burnett-3]

Hi, I would like to run some Box and Whisper plots in SPSS but suppress
the inclusion of outliers in the chart? Is this possible?

Thanks


Jamie



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[Christopher Stride]

I believe it's box and *whisker* ;-)

One (ratrher tedious) way of doing it would be to run the chart, and
then edit it changing the font colours of the outlier markers to the
background colour!




Jamie Burnett wrote:

> Hi, I would like to run some Box and Whisper plots in SPSS but suppress
> the inclusion of outliers in the chart? Is this possible?
>
> Thanks
>
>
> Jamie
>
>
>
> ============================
> This e-mail and all attachments it may contain is confidential and intended solely for the use of the individual to whom it is addressed. Any views or opinions presented are solely those of the author and do not necessarily represent those of Ipsos MORI and its associated companies. If you are not the intended recipient, be advised that you have received this e-mail in error and that any use, dissemination, printing, forwarding or copying of this e-mail is strictly prohibited. Please contact the sender if you have received this e-mail in error.
> ============================
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"Watford FC Supporters - South Yorkshire branch"

[Jamie Burnett-3]

Thanks but I have found a add-on that seems to do the job, have attached
link in case your interested.

http://peltiertech.com/Excel/Charts/BoxWhisker.html

Thanks

Jamie



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[Antonio Maurandi Lopez]

Makes sense.  If you compute one split-half reliability and then
randomly divide the items into another set of split halves and
recompute, and keep doing this until we have computed all possible split
half estimates of reliability. Cronbach's Alpha is mathematically
equivalent to the average of all possible split-half estimates.
So, if you've got a computer better use Cronbach.

Antonio Maurandi




Art Kendall escribió:

> Split half-reliability was done in the days of hand computation to
> estimate internal consistency.
>
> It is pretty much a historical artifact.   It is twenty or twenty-five
> years since I have seen it actually used.
>
> Since you are posting on The SPSS list, I suggest you use Cronbach's
> alpha from the RELIABILITY procedure.
>
> Art Kendall
> Social Research Consultants
>
> AR wrote:
>
>> Dear list:
>>
>>    When testing for split-half reliability is it a good number a
>> Spearman-Brown Coefficient of 0.88?
>> n=1300. and I have 16 items in my questionnaire.
>>
>> Thank you in advance.
>>
>>
>

[Beadle, ViAnn]

It's a bit easier to change the border color of the marker to null. Also you need to suppress the data value labels. Once you do this you can save a chart template checking off the boxes for data element style, data value labels, etc. Then, set this before you run your boxplots. Be sure to only check off these options in the template.

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Synthetic Sheffield
Sent: Monday, December 04, 2006 9:53 AM
To: [hidden email]
Subject: Re: Box and Whisper plots in SPSS

I believe it's box and *whisker* ;-)

One (ratrher tedious) way of doing it would be to run the chart, and
then edit it changing the font colours of the outlier markers to the
background colour!




Jamie Burnett wrote:

> Hi, I would like to run some Box and Whisper plots in SPSS but suppress
> the inclusion of outliers in the chart? Is this possible?
>
> Thanks
>
>
> Jamie
>
>
>
> ============================
> This e-mail and all attachments it may contain is confidential and intended solely for the use of the individual to whom it is addressed. Any views or opinions presented are solely those of the author and do not necessarily represent those of Ipsos MORI and its associated companies. If you are not the intended recipient, be advised that you have received this e-mail in error and that any use, dissemination, printing, forwarding or copying of this e-mail is strictly prohibited. Please contact the sender if you have received this e-mail in error.
> ============================
>

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"Watford FC Supporters - South Yorkshire branch"

[Swank, Paul R]

Actually, Cronbach's Alpha is equivalent to the average of all Guttman-Flanagan split halves. Spearman-Brown coefficients, since they assume parallelness, tend to over estimate the split half reliability when the halves aren't parallel. The Guttman-Flanagan split half does not assume parallelness but assumes the halves are essentially Tau equivalent, the same assumption Cronbach's alpha makes about items. In fact, the Guttman-Flanagan split half is the alpha formula applied to the halves.


Paul R. Swank, Ph.D.
Professor, Developmental Pediatrics
Director of Research,
Children's Learning Center
University of Texas Health Science Center at Houston

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Antonio Maurandi Lopez
Sent: Monday, December 04, 2006 10:12 AM
To: [hidden email]
Subject: Re: split-half reliability

Makes sense.  If you compute one split-half reliability and then randomly divide the items into another set of split halves and recompute, and keep doing this until we have computed all possible split half estimates of reliability. Cronbach's Alpha is mathematically equivalent to the average of all possible split-half estimates.
So, if you've got a computer better use Cronbach.

Antonio Maurandi




Art Kendall escribió:

> Split half-reliability was done in the days of hand computation to
> estimate internal consistency.
>
> It is pretty much a historical artifact.   It is twenty or twenty-five
> years since I have seen it actually used.
>
> Since you are posting on The SPSS list, I suggest you use Cronbach's
> alpha from the RELIABILITY procedure.
>
> Art Kendall
> Social Research Consultants
>
> AR wrote:
>
>> Dear list:
>>
>>    When testing for split-half reliability is it a good number a
>> Spearman-Brown Coefficient of 0.88?
>> n=1300. and I have 16 items in my questionnaire.
>>
>> Thank you in advance.
>>
>>
>

[Peck, Jon]

But please note, a box and whisker chart without the outliers could be rather misleading (which is why SPSS does not offer it directly).  People looking at it would be likely to think that there are no outliers, since the standard chart includes them.  You should probably have a prominent label indicating that they have been excluded.

Regards,
Jon Peck

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Beadle, ViAnn
Sent: Monday, December 04, 2006 10:15 AM
To: [hidden email]
Subject: Re: [SPSSX-L] Box and Whisper plots in SPSS

It's a bit easier to change the border color of the marker to null. Also you need to suppress the data value labels. Once you do this you can save a chart template checking off the boxes for data element style, data value labels, etc. Then, set this before you run your boxplots. Be sure to only check off these options in the template.

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Synthetic Sheffield
Sent: Monday, December 04, 2006 9:53 AM
To: [hidden email]
Subject: Re: Box and Whisper plots in SPSS

I believe it's box and *whisker* ;-)

One (ratrher tedious) way of doing it would be to run the chart, and
then edit it changing the font colours of the outlier markers to the
background colour!




Jamie Burnett wrote:

> Hi, I would like to run some Box and Whisper plots in SPSS but suppress
> the inclusion of outliers in the chart? Is this possible?
>
> Thanks
>
>
> Jamie
>
>
>
> ============================
> This e-mail and all attachments it may contain is confidential and intended solely for the use of the individual to whom it is addressed. Any views or opinions presented are solely those of the author and do not necessarily represent those of Ipsos MORI and its associated companies. If you are not the intended recipient, be advised that you have received this e-mail in error and that any use, dissemination, printing, forwarding or copying of this e-mail is strictly prohibited. Please contact the sender if you have received this e-mail in error.
> ============================
>

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"Watford FC Supporters - South Yorkshire branch"

[Melissa Ives]

You could identify and exclude the outliers in syntax prior to creating
the plot.

Melissa

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of
Jamie Burnett
Sent: Monday, December 04, 2006 8:15 AM
To: [hidden email]
Subject: [SPSSX-L] Box and Whisper plots in SPSS

Hi, I would like to run some Box and Whisper plots in SPSS but suppress
the inclusion of outliers in the chart? Is this possible?

Thanks


Jamie



============================
This e-mail and all attachments it may contain is confidential and
intended solely for the use of the individual to whom it is addressed.
Any views or opinions presented are solely those of the author and do
not necessarily represent those of Ipsos MORI and its associated
companies. If you are not the intended recipient, be advised that you
have received this e-mail in error and that any use, dissemination,
printing, forwarding or copying of this e-mail is strictly prohibited.
Please contact the sender if you have received this e-mail in error.
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