Re: st: factor analysis - calculating Crohnbach's alpha

[Joerg Luedicke <joerg.luedicke@gmail.com>]

On Tue, Oct 9, 2012 at 3:12 PM, Kerry MacQuarrie
<Kerry.MacQuarrie@icfi.com> wrote:
It seems to me that SPSS automatically generated a table with each
factor and its items' factor loadings and the Crohnbach's alpha for
each factor.

I don't even see how that would be possible? How would SPSS select the
variables for calculating Cronbach's alpha?

For example, if we do:

*-----------------------------------------------------------------------
use http://www.stata-press.com/data/r11/bg2.dta, clear
fact  bg2cost1 bg2cost2 bg2cost3 bg2cost4 bg2cost5 bg2cost6, pcf
rot, oblique promax
*-----------------------------------------------------------------------

we get:

    -------------------------------------------------
        Variable |  Factor1   Factor2 |   Uniqueness
    -------------+--------------------+--------------
        bg2cost1 |   0.6998    0.2646 |      0.4775
        bg2cost2 |   0.0244    0.7163 |      0.4898
        bg2cost3 |   0.0244    0.7840 |      0.3886
        bg2cost4 |  -0.1212    0.5652 |      0.6521
        bg2cost5 |   0.7257   -0.0844 |      0.4539
        bg2cost6 |   0.7346   -0.1178 |      0.4290

Now, which of the items would you use for scale 1 and scale 2? And
which ones would SPSS use? I feel the only way of automating this
would be to define some arbitrary thresholds which I would consider as
either bad or more time consuming than an extra command line (because
you would have to run it more than once in order to figure out what
you would regard a reasonable threshold).

Joerg
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/