Why is it easier for psychologists to predict group rather than individual behavior? what are four goals of psychology?

It is easier for psychologists to predict group behavior rather than individual behavior because individuals vary in their behavior whereas groups tend to display the same behavior.

The four primary goals of psychology are to describe, explain, predict, and change behavior.

Through describing the behavior of humans and other animals, we are better able to understand it and gain a better perspective on what is considered normal and abnormal. Psychologists are also interested in explaining behavior in addition to merely describing it. Why do people do the things they do? What factors contribute to development, personality, social behavior, and mental health problems? Psychologists make predictions about how we think and act. Once we understand more about what happens and why it happens, we can use that information to make predictions about when, why, and how it might happen again in the future. Psychology strives to change, influence, or control behavior to make constructive and lasting changes in people's lives.

the factors that the economies of the muslim empires prosper were:

1- land trade routes-located between three continents  

2- sea trade routes

trade contributed to the spread of muslim empires, and with that islamic culture led to a growing feeling of internationalism resulted in the transfer of technology, science, and other cultural forms.