Randomized control trials that have been commonly utilized in the field of medicine and have been used more in recent years in development. Their extensive use is linked to their usefulness. They help us understand what interventions work and what interventions do not. With knowledge gleaned from randomized control trials, we can construct a list of best practices for a particular field and help to maximize practitioners’ impact.Item response theory is a methodology in the human sciences that analyzes questionnaires to make them suitable instruments for measurement. Over the last two years, we used IRT to measure knowledge and attitudes about HIV/AIDS in Ivory Coast, Ethiopia and Kenya and to assess the effectiveness of various forms of medical and social intervention. IRT is useful in measuring many latent or hidden traits, such as the attitudes and emotional instability of war veterans who are at high risk for suicide.