Transition Probabilities of Sc i and Sc ii and Scandium Abundances in the Sun, Arcturus, and HD 84937

New branching fraction (BF) measurements for lines of Sc I and Sc II from 24 Fourier transform spectra calibrated using standard lamps and the Ar branching ratio method are reported. The BFs for 259 lines are converted to absolute atomic transition probabilities using published radiative lifetimes from laser-induced fluorescence measurements. Detailed comparison to earlier published BF measurements corroborates most of the earlier results, with the exception of the yellow-line multiplet of Sc II near 17,500 cm(-1) or approximate to 5700 angstrom. The BFs of lines in this multiplet are found to be systematically too small by several error bars in earlier research. These new lab data on Sc, as well as recent hyperfine-structure studies, are applied to determine the abundance of scandium in the Sun, Arcturus, and HD 84937. General agreement is found with previous scandium abundance determinations in these stars. New consideration of scandium in metal-poor stars confirms that Sc abundances are correlated with Ti and V abundances.