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Situational And Contingency Theory
Situational theory occurred as the response to the trait theory of leadership. Spencer (1884) claimed that the times establish the person and not the other way around. The assumption of this theory is that the divergent circumstances request different typical of one’s; this theory pointed out that there is no single optimum psychographic profile of a leader exists. According to the theory, what an individual actually does when acting as a leader is in enormous part dependent upon characteristics of the circumstances/situation in which he functions. The theorists delineated the style of leadership as contingent to the circumstances/situation, which sometimes relegated as contingency theory.
Functional Theory
A particular useful theory to address specific behaviors of leaders expected to contribute to organizational or unit effectiveness is refers to the functional leadership theory according to Hackman & Walton (1986) and McGrath (1962).  The argument of this theory is that the leaders’ primary job is to examine whatever is indispensable to the group needs is taken care of; thus it can be said that the leaders have done well their job when they have contributed to group effectiveness and cohesion (Fleishmena et.al., 1991, Hacman & Wageman, 2005, Hackman & Walton, 1986).
Transactional and Transformational Theory
        Burns, 1978 pointed out that the transactional leaders are granted power to execute special tasks and reward or punish for the team’s execution/performance. Leaders are granted power in order to evaluate, correct and train the followers when the productivity is not up to the desired level and reward effectiveness when expected outcome is reached. A leader that implements this theory tend to motivates the team to be efficient and effective. The best way for achieving the final desired outcome or goal is communication.


References:
https://shodhganga.inflibnet.ac.in/bitstream/10603/1991/18/18_chapter%203.pdf