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From |
"Verkuilen, Jay" <JVerkuilen@gc.cuny.edu> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: constructing a scale from factor analysis |

Date |
Thu, 31 Jul 2008 13:59:27 -0400 |

Benjamin Highton wrote: >>I assume that there is a simple way to do this, but I haven't been able to find out how. I would like to construct a scale based on n items where each item is weighted in proportion to its factor loading. My clunky way of doing it is to construct the scale myself by (a) accessing the matrix of loadings e(L), (b) multipling each item by its loading, and (c) adding them up. Any advice about a simpler way to do this will be greatly appreciated.<< You want factor scoring, available in postestimation. Weighting by the loadings is not equivalent. One thing I should note is that you are often better off not differentially weighting. Simple sum scores often do better on replication, are much easier to give to other people to use. A mathematically equivalent and often better method is to use average scoring which has the benefit of being in the metric of the original responses, assuming that the original responses are on the same scale. If the loadings and uniquenesses are roughly the same, the reliability of the factor score is going to be only slightly higher than that of the simple sum scores. Average scoring is just (sum score)/K, where K is the number of indicators, and it has the same reliability, being a linear transformation of the sum score. May I suggest getting a copy of the best "user's guide" factor analysis book: R. P. McDonald (1985), Factor Analysis and Related Methods, Erlebaum? (aka "Old MacDonald's FARM"---he'd hit me with his cane if he heard that) * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: constructing a scale from factor analysis***From:*Benjamin Highton <bhighton@ucdavis.edu>

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