Statistical Methods for Psychology

squared semipartial correlation, it is the additional amount that LogPctSAT explains rela- tive tothe amount that Expend left to ...

( or ) to be positive. Occasionally, however, a regression coefficient in this situation will be significantlynegative. Such a v ...

The first step in examining the data has already been carried out in Figure 15.1 with graphical presentations of important varia ...

large residuals (they lie far from the regression line). Such points may represent random error, they may be data that are incor ...

542 Chapter 15 Multiple Regression If the data met the underlying assumptions, we would expect the values of Yto be normally dis ...

not shown in Exhibit 15.1, but came from that SPSS analysis.^8 These values are obtained by choosing the “Save” option in the re ...

On the right of Figure 15.6 you can see that both sets of residuals were reasonably normal, which is important. Cohen et al. (20 ...

Salary than we do with a model that does not include either PTratio or Salary but does in- clude the other two predictors. In th ...

for the two models. Instead we are going to use Akaike’s Information Criterion (AIC), which is based on a likelihood ratio stati ...

must raise the issue of whether this whole approach is generally appropriate. In many cases it is not. If we assume that you hav ...

The major disadvantage of all subsets regression, aside from the enormous amount of computer time it can involve, is the fact th ...

Stepwise Regression The stepwise regressionmethod is more or less the reverse of the backward elimination method.^11 However, be ...

first set. We then apply the regression coefficients obtained from that sample against the data in the other sample to obtain pr ...

15.12 The “Importance” of Individual Variables When an investigator derives a regression equation to predict some criterion on t ...

Another measure of importance, which has much to recommend it, is the squared semi- partial correlation between predictor iand t ...

The answer is that we would probably lose very little. Excellent discussions of this prob- lem are given by Cohen et al. (2003), ...

mediator. (If the mediator is not associated with the independent variable, then it couldn’t mediate anything.) The next step is ...

The first model in the previous table uses maternal care as the sole predictor. The sec- ond model has added self-esteem as a pr ...

The important statistics from the two regressions are shown in Table 15.4. Because SPSS does not report the standard error of Be ...

can conclude that we have convincing evidence of a strong mediating pathway from maternal care through self-esteem to self-effic ...