a maths question

In a workplace of 30 people , random drug testing was done by placing 30 marbles in a bag. 25 white and 5 black.

Each employee would take one marble from the bag, anyone taking a black marble was tested for drugs.

A fellow employee told me that it is best to wait at the end of the queue, as it was less likely to pick a black marble.

Can anyone confirm his theory that; standing at the end of the queue one is less likely to choose a black marble ?