With the continuing surge in the number of mergers and acquisitions in 2007, research effort has been devoted to determining whether the size of an acquisi- tion has an effect on stockholders' abnormal returns (in percent) following the announcement of an impending acquisition.12 Given the data below about abnormal stockholder returns for three size groups of acquired ?rms, test for equality of mean abnormal return.

Large: 11.9, 13.2, 8.7, 9.8, 12.1, 8.8, 10.3, 11.0

Medium: 8.6, 8.9, 5.3, 4.1, 6.2, 8.1, 6.0, 7.1

Small: 5.2, 4.1, 8.8, 10.7, 12.6, 13.0, 9.1, 8.0