Vertical difference, which measures distance between estimated and actual cost for every single observation is classified as

residual term
positive term
negative term
squared term

The correct answer is A. residual term.

A residual term is the difference between an observed value and the value predicted by a model. In the case of a cost function, the residual term is the difference between the actual cost and the estimated cost.

A positive term is a term in an equation that is greater than zero. A negative term is a term in an equation that is less than zero. A squared term is a term in an equation that is the square of another term.

In the case of a cost function, the residual term is not a positive term, a negative term, or a squared term. It is simply the difference between the actual cost and the estimated cost.