Think about the statistic you hear on TV… 4 out of 5 dentist prefer Trident gum over other brands. Is this true? Where did they come up with this?

Think about the statistic you hear on TV… 4 out of 5 dentist prefer Trident gum over other brands. Is this true? Where did they come up with this? What if they only had a sample size of 200 dentists and all of those dentists in their sample were interviewed immediately after leaving a free promotional event sponsored by Trident? Would that seem legitimate to you?