the variables are all expressed in standard-deviation units. All three types of literacy have statistically significant associations with the correlates. The effect of document literacy is much less than that of prose or quantitative literacy and the effect of prose literacy is slightly larger than that of quantitative literacy. Model fit deteriorates markedly, however, if the effect of either document or quantitative literacy is ignored.
Thus, while the panel notes the apparently prime importance of prose literacy, the other dimensions should not be ignored, and for some purposes it may be useful to construct a composite of the three literacy scores. It is not clear how to interpret the separate effects of the three literacy dimensions because they are so highly confounded by design in NALS and NAAL. That is, as long as the same task yields items scored on multiple dimensions, prose, document, and quantitative scores are intrinsically confounded.
Hauser, R.M., and Goldberger, A.S, (1971). The treatment of unobservable variables in path analysis. In H.L. Costner (Ed.), Sociological methodology 1971 (pp. 81-117). San Francisco: Jossey-Bass.
Joreskog, KG., and Goldberger, A.S. (1975). Estimation of a model with multiple indicators and multiple causes of a single latent variable. Journal of the American Statistical Association, 70, 631-639.