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Example
10
Simultaneous Analysis of Several
Groups
Introduction
This example demonstrates how to fit a model to two sets of data at once. Amos is
capable of modeling data from multiple groups (or samples) simultaneously. This
multigroup facility allows for many additional types of analyses, as illustrated in the
next several examples.
Analysis of Several Groups
We return once again to Attig’s (1983) memory data from young and old subjects,
which were used in Example 1 through Example 3. In this example, we will compare
results from the two groups to see how similar they are. However, we will not compare
the groups by performing separate analyses for old people and young people. Instead,
we will perform a single analysis that estimates parameters and tests hypotheses about
both groups at once. This method has two advantages over doing separate analyses for
the young and old groups. First, it provides a test for the significance of any
differences found between young and old people. Second, if there are no differences
between young and old people or if the group differences concern only a few model
parameters, the simultaneous analysis of both groups provides more accurate
parameter estimates than would be obtained from two separate single-group analyses.