Python for SPSS
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Does anyone know an introduction (tutorial) to 'python for SPSS' (not simply python) for someone who is not the most professional programmer: book or video
thank you
Dr. Frank Gaeth
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The Programming and Data Management book
available in the articles section of the SPSS Community site (www.ibm.com/developerworks/spssdevcentral)
shows the basics of using Python with SPSS, including the most important
language constructs and the apis you use to interact with SPSS. It
has many short examples of doing typical SPSS tasks.
HTH, Jon Peck Senior Software Engineer, IBM [hidden email] 312-651-3435 From: drfg2008 <[hidden email]> To: [hidden email] Date: 02/16/2011 08:56 AM Subject: [SPSSX-L] Python for SPSS Sent by: "SPSSX(r) Discussion" <[hidden email]> Does anyone know an introduction (tutorial) to 'python for SPSS' (not simply python) for someone who is not the most professional programmer: book or video thank you ----- Free University Berlin -- View this message in context: http://spssx-discussion.1045642.n5.nabble.com/Python-for-SPSS-tp3387662p3387662.html Sent from the SPSSX Discussion mailing list archive at Nabble.com. ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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In reply to this post by drfg2008
I'm biased because the writers are coworkers, but have found the documentation available on developerWorks very useful to get up and running with Python. There are lots of examples, and you can often find code reasonably similar to what you want to do and and just tweak it. The only "problem" is that there's so much information up there that it can be like drinking from a fire hose. Alex https://www.ibm.com/developerworks/mydeveloperworks/groups/service/html/communityview?communityUuid=ab16c38e-2f7b-4912-a47e-85682d124d32
Does anyone know an introduction (tutorial) to 'python for SPSS' (not simply python) for someone who is not the most professional programmer: book or video thank you |
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"drinking from a fire hose", LOL, good one! My starting point was http://docs.python.org/tutorial/, then the data management book, then lots of other stuff. The Python Tutor mailing list is also useful. Albert-Jan ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ From: Alex Reutter <[hidden email]> To: [hidden email] Sent: Wed, February 16, 2011 3:20:20 PM Subject: Re: [SPSSX-L] Python for SPSS I'm biased because the writers are coworkers, but have found the documentation available on developerWorks very useful to get up and running with Python. There are lots of examples, and you can often find code reasonably similar to what you want to do and and just tweak it. The only "problem" is that there's so much information up there that it can be like drinking from a fire hose. Alex https://www.ibm.com/developerworks/mydeveloperworks/groups/service/html/communityview?communityUuid=ab16c38e-2f7b-4912-a47e-85682d124d32
Does anyone know an introduction (tutorial) to 'python for SPSS' (not simply python) for someone who is not the most professional programmer: book or video thank you |
Two-item scale and Cronbach alpha
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Hi dear all,
I am using a two-item scale and would like to know how to assess internal consistency of this case. I saw in some journals that some authors only report Pearson correlation between the items as an assessment of internal consistency two-item scales. Any idea ? Any reference ? Thanks in advance. Best, Mbaye. |
Re: Two-item scale and Cronbach alpha
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No reference available, but simply because Cronbach's alpha for two
items is identical to Pearson correlation. On Wed, Feb 16, 2011 at 15:43, Mbaye Fall Diallo <[hidden email]> wrote: > Hi dear all, > I am using a two-item scale and would like to know how to assess internal > consistency of this case. I saw in some journals� that some authors only > report Pearson correlation between the items as an assessment of internal > consistency two-item scales. Any idea ? Any reference ? > Thanks in advance. > > Best, > Mbaye. -- ___________________________________________________________________ Maurice Vergeer Department of communication Radboud University� (www.ru.nl) PO Box 9104 NL-6500 HE Nijmegen The Netherlands Visiting Professor Yeungnam University, Gyeongsan, South Korea contact: E: [hidden email] T: +31 24 3612297 (direct)/ 3612372 (secretary) / maurice.vergeer (skype) personal webpage: www.mauricevergeer.nl blog:� http://blog.mauricevergeer.nl/ Journalism: www.journalisteninhetdigitaletijdperk.nl Recent publications (see complete list at www.mauricevergeer.nl/node/2): -Vergeer, M., Hermans, L., & Sams, S. (accepted for publication). Online social networks and micro-blogging in political campaigning: The exploration of a new campaign tool and a new campaign style. Party Politics. -Eisinga, R., Franses, Ph.H., & Vergeer, M. (2010). Weather conditions and daily television use in the Netherlands, 1996–2005. International Journal of Meteorology. ___________________________________________________________________ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
Re: Two-item scale and Cronbach alpha
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really?
I'd say that in this two-item case standardized alpha is always higher than pearson, except for cases in which r = 1.00 (= alpha). Matthias On Wed, Feb 16, 2011 at 3:50 PM, Maurice Vergeer <[hidden email]> wrote: No reference available, but simply because Cronbach's alpha for two |
Re: Two-item scale and Cronbach alpha
Administrator
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In reply to this post by Maurice Vergeer
"Conceptually, both equations [i.e., KR-20 and Cronbach's alpha] give the average of all of the possible split-half reliabilities of a scale."
Source: Streiner DL, Norman GR (2008). "Health Measurement Scales" (4th Ed.). Oxford Univ. Press. (p. 90).
--
Bruce Weaver bweaver@lakeheadu.ca http://sites.google.com/a/lakeheadu.ca/bweaver/ "When all else fails, RTFM." PLEASE NOTE THE FOLLOWING: 1. My Hotmail account is not monitored regularly. To send me an e-mail, please use the address shown above. 2. The SPSSX Discussion forum on Nabble is no longer linked to the SPSSX-L listserv administered by UGA (https://listserv.uga.edu/). |
Re: Two-item scale and Cronbach alpha
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In reply to this post by Mbaye Fall Diallo
Like many other measures of reliability alpha is the
ratio of true variance to total variance.
A key term in alpha is the average of the unique interitem correlations. When there is only 1 unique correlation that correlation is the average correlation. It would require some calculation to see what the alpha would be when all that is presented is the correlation. see the syntax below to see an example of how to calculate alpha given the number of items and the average interitem correlation. Open a new instance of SPSS. Paste the syntax below into a syntax window. Run it. Art Kendall Social Research Consultants data list list /meanr (f5.2). begin data. .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 end data. compute k=2. variable labels meanr 'mean of upper triangular r matrix among items' k 'number of item in this instance 2'. compute numerator = k * meanr. compute denominator = (1+(k-1)*meanr). compute alpha = numerator /denominator. var labels numerator '"true" variance'/ denominator '"total" variance' alpha 'proportion of total variance that is true variance'. list. On 2/16/2011 9:43 AM, Mbaye Fall Diallo wrote: Hi dear all,===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
Art Kendall
Social Research Consultants |
Re: Two-item scale and Cronbach alpha
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If I'm correct this is also known as the Spearman-Brown formula?
On Wed, Feb 16, 2011 at 20:04, Art Kendall <[hidden email]> wrote: > Like many other measures of reliability alpha is the ratio of true variance > to total variance. > A key term in alpha is the average of the unique interitem correlations. > When there is only 1 unique correlation that correlation is the average > correlation. It would require some calculation to see what the alpha would > be when all that is presented is the correlation. > > see the syntax below to see an example of how to calculate alpha given the > number of items and the average interitem correlation. > > Open a new instance of SPSS.� Paste the syntax below into a syntax window. > Run it. > > Art Kendall > Social Research Consultants > > data list list /meanr (f5.2). > begin data. > .1 > .2 > .3 > .4 > .5 > .6 > .7 > .8 > .9 > 1.0 > end data. > compute k=2. > variable labels meanr 'mean of upper triangular r matrix among items' > � k 'number of item in this instance 2'. > compute numerator = k * meanr. > compute denominator = (1+(k-1)*meanr). > compute alpha = numerator /denominator. > var labels > � numerator '"true" variance'/ > � denominator '"total" variance' > � alpha 'proportion of total variance that is true variance'. > list. > > On 2/16/2011 9:43 AM, Mbaye Fall Diallo wrote: > > Hi dear all, > I am using a two-item scale and would like to know how to assess internal > consistency of this case. I saw in some journals� that some authors only > report Pearson correlation between the items as an assessment of internal > consistency two-item scales. Any idea ? Any reference ? > Thanks in advance. > > Best, > Mbaye. > > ===================== To manage your subscription to SPSSX-L, send a message > to [hidden email] (not to SPSSX-L), with no body text except the > command. To leave the list, send the command SIGNOFF SPSSX-L For a list of > commands to manage subscriptions, send the command INFO REFCARD -- ___________________________________________________________________ Maurice Vergeer Department of communication Radboud University� (www.ru.nl) PO Box 9104 NL-6500 HE Nijmegen The Netherlands Visiting Professor Yeungnam University, Gyeongsan, South Korea contact: E: [hidden email] T: +31 24 3612297 (direct)/ 3612372 (secretary) / maurice.vergeer (skype) personal webpage: www.mauricevergeer.nl blog:� http://blog.mauricevergeer.nl/ Journalism: www.journalisteninhetdigitaletijdperk.nl Recent publications (see complete list at www.mauricevergeer.nl/node/2): -Vergeer, M., Hermans, L., & Sams, S. (accepted for publication). Online social networks and micro-blogging in political campaigning: The exploration of a new campaign tool and a new campaign style. Party Politics. -Eisinga, R., Franses, Ph.H., & Vergeer, M. (2010). Weather conditions and daily television use in the Netherlands, 1996–2005. International Journal of Meteorology. ___________________________________________________________________ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
Re: Two-item scale and Cronbach alpha
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If I recall correctly Spearman-Brown is the same,
but in use is more often rearranged to estimate how many more
items would needed to achieve a given level of reliability.� If it
is important you might want to check this since I last studied
this in 1972.
Art Kendall Social Research Consultants On 2/16/2011 2:41 PM, Maurice Vergeer wrote: ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARDIf I'm correct this is also known as the Spearman-Brown formula? On Wed, Feb 16, 2011 at 20:04, Art Kendall [hidden email] wrote:Like many other measures of reliability alpha is the ratio of true variance to total variance. A key term in alpha is the average of the unique interitem correlations. When there is only 1 unique correlation that correlation is the average correlation. It would require some calculation to see what the alpha would be when all that is presented is the correlation. see the syntax below to see an example of how to calculate alpha given the number of items and the average interitem correlation. Open a new instance of SPSS.� Paste the syntax below into a syntax window. Run it. Art Kendall Social Research Consultants data list list /meanr (f5.2). begin data. .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 end data. compute k=2. variable labels meanr 'mean of upper triangular r matrix among items' � k 'number of item in this instance 2'. compute numerator = k * meanr. compute denominator = (1+(k-1)*meanr). compute alpha = numerator /denominator. var labels � numerator '"true" variance'/ � denominator '"total" variance' � alpha 'proportion of total variance that is true variance'. list. On 2/16/2011 9:43 AM, Mbaye Fall Diallo wrote: Hi dear all, I am using a two-item scale and would like to know how to assess internal consistency of this case. I saw in some journals� that some authors only report Pearson correlation between the items as an assessment of internal consistency two-item scales. Any idea ? Any reference ? Thanks in advance. Best, Mbaye. ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD-- ___________________________________________________________________ Maurice Vergeer Department of communication Radboud University� (www.ru.nl) PO Box 9104 NL-6500 HE Nijmegen The Netherlands Visiting Professor Yeungnam University, Gyeongsan, South Korea contact: E: [hidden email] T: +31 24 3612297 (direct)/ 3612372 (secretary) / maurice.vergeer (skype) personal webpage: www.mauricevergeer.nl blog:� http://blog.mauricevergeer.nl/ Journalism: www.journalisteninhetdigitaletijdperk.nl Recent publications (see complete list at www.mauricevergeer.nl/node/2): -Vergeer, M., Hermans, L., & Sams, S. (accepted for publication). Online social networks and micro-blogging in political campaigning: The exploration of a new campaign tool and a new campaign style. Party Politics. -Eisinga, R., Franses, Ph.H., & Vergeer, M. (2010). Weather conditions and daily television use in the Netherlands, 1996–2005. International Journal of Meteorology. ___________________________________________________________________ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
Art Kendall
Social Research Consultants |
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In reply to this post by Art Kendall
Just to reinforce what Art has written below: there are
a few different formulas
for calculating Cronbach's alpha and the form of the equation provided below helps one to see the relationship of alpha to the interitem correlations. With two items, the formula reduces to Alpha = 2r / (1 + r) Where r is the Pearson r between the two items. In a case like this, one can calculate the Pearson r and use it as a measure of reliability but it would be a different type of measure than alpha. It should be noted that the UCLA "Academic Technology Services" has a great website that provide info on SPSS and other packages. One of the FAQs they answer about SPSS is what does Cronbach's alpha mean. An earlier version of the answer provided the formula that Art uses below. I just checked the page and it has been updated and the formula converted to use covariances and variances; see: http://www.ats.ucla.edu/stat/spss/faq/alpha.html However, it should also be pointed out that a numbre of people are dissatistfied with the use of Cronbach's alpha as a measure of reliability or consistency. Many of these can found over on the Structural Equation Modeling (SEM) mailing list, SEMNET. Cameron Macintosh posts much useful information there as well a providing the following references that take a dim view of Cronbach's alpha -- one might one to review some of these to understand the current issues regarding alpha: Sijtsma, K. (2009). On the use, the misuse, and the very limited usefulness of Cronbach's alpha. Psychometrika, 74(1), 107-120. Bentler, P.M. (2009). Alpha, dimension-free, and model-based internal consistency reliability. Psychometrika, 74(1), 137-143. Green, S.B., & Yang, Y. (2009). Commentary on coefficient alpha: a cautionary tale. Psychometrika, 74(1), 121-135. Yang, Y., & Green, S.B. (2010). A note on structural equation modeling estimates of reliability. Structural Equation Modeling, 17(1), 66-81. Ogasawara, H. (2009). On the estimators of model-based and maximal reliability. Journal of Multivariate Analysis, 100(6), 1232-1244. Huysamen, G.K. (2006). Coefficient alpha: Unnecessarily ambiguous, unduly ubiquitous. SA Journal of Industrial Psychology, 32(4), 34-40. -Mike Palij New York University
----- Original Message ----- From: Art Kendall To: [hidden email] Sent: Wednesday, February 16, 2011 2:04 PM Subject: Re: Two-item scale and Cronbach alpha Like many other measures of reliability alpha is the ratio of true variance to total variance. A key term in alpha is the average of the unique interitem correlations. When there is only 1 unique correlation that correlation is the average correlation. It would require some calculation to see what the alpha would be when all that is presented is the correlation. see the syntax below to see an example of how to calculate alpha given the number of items and the average interitem correlation. Open a new instance of SPSS. Paste the syntax below into a syntax window. Run it. Art Kendall Social Research Consultants data list list /meanr (f5.2). begin data. .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 end data. compute k=2. variable labels meanr 'mean of upper triangular r matrix among items' k 'number of item in this instance 2'. compute numerator = k * meanr. compute denominator = (1+(k-1)*meanr). compute alpha = numerator /denominator. var labels numerator '"true" variance'/ denominator '"total" variance' alpha 'proportion of total variance that is true variance'. list. On 2/16/2011 9:43 AM, Mbaye Fall Diallo wrote: Hi dear all, I am using a two-item scale and would like to know how to assess internal consistency of this case. I saw in some journals that some authors only report Pearson correlation between the items as an assessment of internal consistency two-item scales. Any idea ? Any reference ? Thanks in advance. Best, Mbaye. ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
Re: Two-item scale and Cronbach alpha
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Thanks to all of you who provided explanations on my post.
Best,
Mbaye, Date: Wed, 16 Feb 2011 15:20:49 -0500 From: [hidden email] Subject: Re: Two-item scale and Cronbach alpha To: [hidden email] Just to reinforce what Art has written below: there are
a few different formulas
for calculating Cronbach's alpha and the form of the equation provided below helps one to see the relationship of alpha to the interitem correlations. With two items, the formula reduces to Alpha = 2r / (1 + r) Where r is the Pearson r between the two items. In a case like this, one can calculate the Pearson r and use it as a measure of reliability but it would be a different type of measure than alpha. It should be noted that the UCLA "Academic Technology Services" has a great website that provide info on SPSS and other packages. One of the FAQs they answer about SPSS is what does Cronbach's alpha mean. An earlier version of the answer provided the formula that Art uses below. I just checked the page and it has been updated and the formula converted to use covariances and variances; see: http://www.ats.ucla.edu/stat/spss/faq/alpha.html However, it should also be pointed out that a numbre of people are dissatistfied with the use of Cronbach's alpha as a measure of reliability or consistency. Many of these can found over on the Structural Equation Modeling (SEM) mailing list, SEMNET. Cameron Macintosh posts much useful information there as well a providing the following references that take a dim view of Cronbach's alpha -- one might one to review some of these to understand the current issues regarding alpha: Sijtsma, K. (2009). On the use, the misuse, and the very limited usefulness of Cronbach's alpha. Psychometrika, 74(1), 107-120. Bentler, P.M. (2009). Alpha, dimension-free, and model-based internal consistency reliability. Psychometrika, 74(1), 137-143. Green, S.B., & Yang, Y. (2009). Commentary on coefficient alpha: a cautionary tale. Psychometrika, 74(1), 121-135. Yang, Y., & Green, S.B. (2010). A note on structural equation modeling estimates of reliability. Structural Equation Modeling, 17(1), 66-81. Ogasawara, H. (2009). On the estimators of model-based and maximal reliability. Journal of Multivariate Analysis, 100(6), 1232-1244. Huysamen, G.K. (2006). Coefficient alpha: Unnecessarily ambiguous, unduly ubiquitous. SA Journal of Industrial Psychology, 32(4), 34-40. -Mike Palij New York University
----- Original Message ----- From: Art Kendall To: [hidden email] Sent: Wednesday, February 16, 2011 2:04 PM Subject: Re: Two-item scale and Cronbach alpha Like many other measures of reliability alpha is the ratio of true variance to total variance. A key term in alpha is the average of the unique interitem correlations. When there is only 1 unique correlation that correlation is the average correlation. It would require some calculation to see what the alpha would be when all that is presented is the correlation. see the syntax below to see an example of how to calculate alpha given the number of items and the average interitem correlation. Open a new instance of SPSS. Paste the syntax below into a syntax window. Run it. Art Kendall Social Research Consultants data list list /meanr (f5.2). begin data. .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 end data. compute k=2. variable labels meanr 'mean of upper triangular r matrix among items' k 'number of item in this instance 2'. compute numerator = k * meanr. compute denominator = (1+(k-1)*meanr). compute alpha = numerator /denominator. var labels numerator '"true" variance'/ denominator '"total" variance' alpha 'proportion of total variance that is true variance'. list. On 2/16/2011 9:43 AM, Mbaye Fall Diallo wrote: Hi dear all, I am using a two-item scale and would like to know how to assess internal consistency of this case. I saw in some journals that some authors only report Pearson correlation between the items as an assessment of internal consistency two-item scales. Any idea ? Any reference ? Thanks in advance. Best, Mbaye. ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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