Beta Weights
Standardized Slope Coefficients
As noted earlier, the slope coefficient b is unstandardized, which means that it is specific to the units in which the IV and DV are measured. There is no way to “eyeball” an unstandardized slope coefficient and assess its strength because there are no boundaries or benchmarks that can be used with unstandardized statistics—they are specific to whatever metric the DV is measured in. The way to solve this is to standardize b. Beta weights range between 0.00 and ±1.00 and, like correlation coefficients, rely more on guidelines than rules for interpretation of their strength. Generally speaking, betas between 0 and ±.19 are considered weak, from about ±.20 to ±.29 are moderate, ±.30 to ±.39 are strong, and anything beyond ±.40 is very strong. These ranges can vary by topic, though; subject-matter experts must decide whether a beta weight is weak or strong within the customs of their fields of study.
Standardization is accomplished as follows:
We saw in the calculation of SEb that the The standard deviation of x is 1.75 and the standard deviation of y
is 317.89. We already computed b and know that it is 134.88. Plugging these numbers into Formula 14(7), we get
In this calculation, rounding would have thrown the final answer off the mark, so the division and multiplication were completed in a single step. The beta weight is .74. If this number seems familiar, it is! The correlation between these two variables is .74. Beta weights will equal correlations (within rounding error) in the bivariate context and can be interpreted the same way. A beta of .74 is very strong.
