It is also the first to conclude definitively outside of a laboratory setting that holding a phone to the ear or talking through a hands-free device pose the same risks.

The authors of this meta-analysis concluded that more studies were needed because of lack of statistical power to conclude definitively about the effect of etomidate on mortality.

Yesterday morning, federal authorities concluded definitively that Mr. Diomande had inhalation anthrax.

But he said there was no way to conclude definitively whether his return to pitching had been rushed.

Based on the third party agreements, the court could not definitively conclude if downloads were licenses.

Both studies failed to conclude definitively whether the fatal bullet, now in three fragments, had been fired by the rifle.

This situation changed in 2011, when a new study of the remains definitively concluded that Gustafson was right as to both the age and the human origin of the point.

In a report last year, the Indian Affairs Committee said it could not "definitively conclude what, if anything, Griles did to assist Mr. Abramoff's clients."

But the agency's analysts have never definitively concluded that he has used doubles to give speeches or make television appearances, where the likeness could be closely studied.

Tonight's announcement, although more definitively concluding his quest for the Oval Office, had a lighter air and a simpler message.