How can understanding point of view and bias help us in historical
investigations?

You can understand why the people or person made the choice that they did and what influenced them to do so.

its main object was the establishment of "settlement houses" in poor urban areas, in which volunteer middle-class "settlement workers" would live, hoping to share knowledge and culture with, and alleviate the poverty of, their low-income neighbors.

the installment plan of the 1920s, an arrangement that allowed people to buy what they wanted with a small down payment and pay off the rest in monthly installments, provided americans a way to own what they did not have the money to buy.