Principals have important management roles, including responsibilities for teachers, curricula and budgets. Schools change principals frequently; about 20% of public school principals in the United States leave their positions each year. Despite the significance of principals and the regularity...

The global commitment to universal access for people in need of antiretroviral therapy has transformed the lives of adolescents with HIV. In contrast, there has been limited commitment at policy or service level to the need for effective therapeutic interventions which can help them to cope with...

There are two non-isomorphic choices of 5 columns and of 6 columns from the 12-run Plackett-Burman design which are essentially identical in terms of E(s2) and extended word length pattern. Surprisingly, in each case one choice is superior to the other for exploring models with main effects and...