Russel-Research-Method-in-Anthropology

Multivariate Analysis 675
BTU and OVER65 show effects on suicide rates that are independent of the
effects of INCOME.
But look what happens when we enter all three independent variables into
the regression. Table 21.21 shows the result: INCOME remains statistically
significant, but neither BTU nor OVER65 are.
TABLE 21.21
Regression of All Three Independent Variables and SUICIDE
Dep Var: SUICIDE N: 51 Multiple R: 0.630 Squared multiple R: 0.397
Adjusted squared multiple R: 0.358 Standard error of estimate: 2.889
Effect Coefficient Std Error Std Coef Tolerance t P (2 Tail)
CONSTANT 26.898 4.806 0.000 . 5.597 0.000
INCOME 0.000 0.000 0.434 0.889 3.613 0.001
BTU 0.004 0.003 0.183 0.714 1.362 0.180
OVER65 0.439 0.228 0.245 0.793 1.927 0.060
If BTU remained statistically significant while OVER65 did not, we could
conclude that OVER65 had no effect on suicide independently of INCOME
and BTU. Likewise, if OVER65 remained statistically significant while BTU
did not, we could conclude that BTU had no effect on suicide independently
of INCOME and OVER65. In this instance, however, we can only conclude
that we have a multicollinearity problem that obscures our findings. We can’t
tell if either BTU or OVER65 has effects on suicide independently of
INCOME. (In fact, the condition index for this regression is 27, which indicates
strong to severe multicollinearity.)
Factor Analysis
Factor analysis is based on the simple and compelling idea that if things we
observe are correlated with each other, they must have some underlying variable
in common. Factor analysis refers to a set of techniques for identifying
and interpreting those underlying variables.
For example, people in the United States who are in favor of gun control
are likely (but not guaranteed) to be in favor of: (1) a woman’s right to an
abortion; (2) participation by the U.S. military in overseas peacekeeping missions
of the United Nations; and (3) affirmative action in college admissions.
People who are against gun control are likely to favor: (1) restrictions on abortion;
(2) less involvement of the United States in UN peacekeeping missions;
and (3) curbs on affirmative action.