Ownership of 51% of a company's outstanding stock guarantees control. But as a practical matter holding as little as 15% to 25% of a widely held company results in effective control.

This statement is true. While owning 51% of a company's outstanding stock guarantees control, even holding a smaller percentage such as 15% to 25% can result in effective control of a widely held company. This can be achieved through alliances with other major shareholders or by exerting influence through voting rights and board representation.