Ability to influence a group is the one's ability to mobilize and leave a positive impact on others by stamping their mind with one's own intelligence, performance, behavior and vibrant personality. To have the ability of influencing a group, one should have believe in thyself and believe in that particular thing which one is trying to do. This means that power of expression is a major factor which contributes towards ability to influence a group.

For Example : -

You have been called for a discussion with students on pressure management. Now this discussion will be successful only when you are able to stamp the minds of students, so that they should feel it as a worth discussion as they have gained a lot from you. Now the question arises, how to stamp their minds indelibly ? For this you require a great power of expression, intelligence, knowledge and behavior.