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help for factortest                                          Joao Pedro Azevedo
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Calculate specification tests before factor or pca

factortest [varlist] [if exp] [in range]

Description

factortest performs the Bartlett's test for sphericity and the
Kaiser-Meyer-Olkin Measure of Sampling Adequacy. Both tests should be
used prior to a factor or a principal component analysis.

Technical details

Determinant of the matrix of correlation: This determinant will equal 1.0
only if all correlations equal 0, otherwise the determinant will be less
than 1.

Bartlett's test for sphericity: Calculates the determinant of the matrix
of the sums of products and cross-products (S) from which the
intercorrelations matrix is derived. The determinant of the matrix S is
converted to a chi-square statistic and tested for significance.

The null hypothesis is that the intercorrelation matrix comes from a
population in which the variables are noncollinear (i.e. an identity
matrix), and that the non-zero correlations in the sample matrix are due
to sampling error.

Kaiser-Meyer-Olkin Measure of Sampling Adequacy: is an index for
comparing the magnitudes of the observed correlation coefficients to the
magnitudes of the partial correlation coefficients.

Large values for the KMO measure indicate that a factor analysis of the
variables is a good idea.

90 or above, excelent
80 or above, meritorious
70 or above, middling
60 or above, mediocre
50 or above, miserable; and
below .50, unacceptable.

Examples

. factortest price mpg rep78 rep77 hdroom rseat trunk

References

Box,G.E.P.(1949) "A general distribution theory for a class of likelihood
criteria." Biometrica, 36: 317-346.

Cureton, E.E., & D'Agostino, R.B. (1983). Factor analysis: An applied
approach. Hillsdale, NJ: Erlbaum.

Authors

Joao Pedro Azevedo, IPEA, Brazil
jazevedo@ipea.gov.br

Aknowledgements

I would like to thank May M. Boggess for her help and Roberto De Miguel
for his suggestions.

Also see

Manual:  [R] factor [R] pca [R] alpha
Online:  help for factor; pca; alpha

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