Table 1shows the regression coefficients and the adjusted
R 2 for linear regressions of CPS
ED for different reading speed criteria (75%–95% of the MRS) versus CPS
TL for regular polarity. The linear regression results for the reverse polarity data set were similar to those for the regular polarity data set and are not shown here. Not surprisingly, the correlations between CPS
ED for different criteria and CPS
TL were high (adjusted
R 2 varies from 0.673 to 0.853 for regular polarity and from 0.653 to 0.765 for reverse polarity). Although regression with a CPS
ED criterion of 75% gave the highest adjusted
R 2 values, CPS
ED criterion of 85% yielded slopes that were closest to 1. A slope of ∼1 makes the conversion between CPS
ED and CPS
TL straightforward as a mere offset (the
y-intercept). For instance, given that the slope is close to 1 for CPS
ED criteria of 80% and 85%, the
y-intercept is approximately the average difference between the CPS
ED and CPS
TL. A CPS
ED criterion of 80% is a good compromise for high adjusted
R 2 and slope ∼1.
Figure 4shows the data and the regression line for CPS
ED with a criterion level of 80% versus CPS
TL for the regular polarity data set.