McClelland's Theory of Needs 

McClelland’s theory of needs proposes achievement, power, and affiliation are three important needs. McClelland’s theory of needs was developed by David McClelland and his associates. Compared to Maslow’s hierarchy, these needs are more akin to motivating factors than strict needs for survival. There are three. Need for achievement (nAch) is the drive to excel, to achieve in relationship to a set of standards.
Need for power (nPow) is the need to make others behave in a way they would not have otherwise. Need for affiliation (nAff) is the desire for friendly and close interpersonal relationships. In general, high achievers perform best when they perceive their probability of success as 50 percent. They like to set goals that require stretching themselves a little. Based on prior nAch research, we can predict some relationships between nAch and job performance. When employees have a high level of nAch, they tend to exhibit more positive moods and be more interested in the task at hand.
The need for achievement has received a great deal of research attention and acceptance in a wide array of fields, including organizational behavior, psychology, and general business. The degree to which we have each of the three needs is difficult to measure, and therefore the theory is difficult to put into practice. A behavior may be directed at satisfying many different needs, and many different behaviors may be directed at satisfying one given need, making needs difficult to isolate and examine. The concepts are helpful, but they are not often used objectively.