Leadership is defined differently by both theorists and the context. As such, there is no broadly accepted definition of leadership; nor should there necessarily be one definition. There are student leaders, production team leaders, community organizing leaders, nonprofit executives, various ranks of military leaders, company CEOs, nonprofit board leaders, teachers as leaders, administration leaders in higher education, grassroots association community leaders, religious leaders and leaders of gender-based men’s and women’s religious groups (monks/nuns), political leaders at various local, state and national contexts, female and male styles, ethnic subcultural influences on leaders, international style differences, traditions within a multitude of indigenous peoples, and so on. As such, one will not encounter a one-size-fits-all leadership instrument. “The design of [a] leadership instrument depends upon the specific leadership theory on which it is based, and will target traits, behaviours, interactions, charisma or other dimensions accordingly. In other words, different leadership instruments measure different leadership facets. It follows that in measuring leadership, the person requiring the measure must understand exactly what is to be measured, and select the appropriate instrument” (Johnson, n.d., 2). For example, House and Aditya (1997) note most leadership studies have focused on supervisory leadership, with the result that most leadership instruments are limited in application to supervisors and managers. In the nearly 2000 pages of the Encyclopedia of Leadership (Goerthals et al., 2004) there is less than one page on measuring leadership. In the same text, Nirenberg (2004) says “If being effective is important, it should be measured” (849), yet he provides little to help guide us. He says followers need to be satisfied and objectives need to be met, regular observable feedback is more likely at the small-group level, and that 360-degree feedback instruments are useful for obtaining feedback from others at all levels. Without 360 measures (other people to rate the leader), there is little to no incentive for followers to push for more effective leadership, because they have no power over their supervisor. Political leadership is different because politicians use polls to solicit information about what their followers want and how they feel about him/her. Nirenberg does provide a long list of personal and interpersonal skills and attributes that contribute to success at the individual level as well, derived from studies of the corporate sector. Regarding evaluating leadership effectiveness in the organizational context, Nirenberg states that the right environment can be determined by surveys and structured action research techniques involving all employees in developing the culture they will find most satisfying and productive (852). Likewise, a search of “Leadership in Nonprofit Organizations: A Reference Handbook” (Agard, 2011) issuing over 1000 pages had no entries at all for “measuring,” “instruments,” or “scales,” nor did articles on theory discuss measurement. Thus the Encyclopedia of Leadership left me feeling somewhat frustrated. It seems it is up to us to determine what we think we should measure in a particular context and look for instruments that are accomplishing that, are tested and valid, as well as affordable. There are no easy paths here. There are some important issues to consider in designing leadership research and deciding which tools may be most appropriate. Day and Antonakis in “The Nature of Leadership” (2012) note that leadership has global, shared, and configural properties that each reflect different forms of aggregation from lower-level units (events, individuals, groups, and organizations). In addition, they cite newer quantitative techniques that can help researchers ask new questions and study traditional leadership questions in novel ways (e.g., latent polynomial regression, multilevel member weighted modeling, intercept as mean latent growth modeling, multilevel SEM, and latent class cluster analysis). The point is that these techniques can be used as means of measuring leadership, especially in complex relationships among numerous variables, in addition to the traditional leadership instruments, which is what this library primarily covers. Likewise, outside the scope of this library are techniques mentioned by Zyphur, Barsky, and Zhang (2012) that may be useful to leadership researchers, such as “agent-based simulations for testing complexity theories of leadership (e.g., Dionne & Dionne, 2008), social networkbased approaches to study shared leadership (e.g., Carson, Tesluk, & Marrone, 2007; Ensley, Hmieleski, & Pearce, 2006), the life narrative method for examining leadership development (e.g., Ligon, Hunter & Mumford, 2008), and various biological approaches (e.g. Zhang, Ilies & Arvey, 2009)” (67).
If you want a relatively simple, straightforward questionnaire that's been used for many years, you could do worse than consider the "Merrill & Reid" social styles exercise. There's lots on the internet about it, so have a Google....