Sunday, December 21, 2008
Bootstrapping
In statistics, bootstrapping is a modern, computer-intensive, general purpose approach to statistical inference, falling within a broader class of resampling methods.
Bootstrapping is the practice of estimating properties of an estimator (such as its variance) by measuring those properties when sampling from an approximating distribution. One standard choice for an approximating distribution is the empirical distribution of the observed data. In the case where a set of observations can be assumed to be from an independent and identically distributed population, this can be implemented by constructing a number of resamples of the observed dataset (and of equal size to the observed dataset), each of which is obtained by random sampling with replacement from the original dataset.
Tuesday, December 16, 2008
Structural Equation Modeling
What is Structural Equation Modeling?
Structural equation modeling, or SEM, is a very general,
chiefly linear, chiefly cross-sectional statistical modeling
technique.Factor analysis, path analysis and regression all
represent special cases of SEM.SEM is a largely confirmatory,
rather than exploratory, technique.That is, a researcher are
more likely to use SEM to determine whether a certain
model is valid.,rather than using SEM to "find" a suitable
model--although SEM analyses often involve a certain exploratory
element.In SEM, interest usuallyfocuses on latent constructs--abstract
psychological variables like "intelligence"or "attitude
toward thebrand"--rather than on the manifest variables
used to measure these constructs.
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