The performance of various shrinkage formulas for estimating the population squared multiple correlation coefficient (ρ2) were compared under extreme conditions often found in educational research with small sample sizes of 10, 15, 20, 25, 30 and regressor variates ranging from 2 to 4. A new formula for estimating ρ2, Adj R2 DW, was examined in terms of its performance under various conditions of N, p, ρ2, along with its bias properties and standard error estimates. The two shrinkage formulas that performed most consistently were the Claudy (Adj R2 C) and Walker (Adj R2 DW)
Walker, David A.
"A Comparison of Eight Shrinkage Formulas under Extreme Conditions,"
Journal of Modern Applied Statistical Methods:
1, Article 16.
Available at: http://digitalcommons.wayne.edu/jmasm/vol6/iss1/16