The dashed segment of the plotted experiment in the graph in the lesson is called an

extrapolation

Explanation:

Its a type of estimation and is beyond the observer's range and is the value of a variable on the basis of the relation to the another variable. It can also be applied to the human experience to project to expand the known experiences. Like the driver interprets the road conditions prior to his visual contact.

The dashed segment of the plotted experiment in the graph in the lesson is called an: Extrapolation.