What is effective / effectiveness?
effective / effectiveness is The degree to which a treatment plan, programme or project has achieved its purpose within the limits set for reaching its objective. For example, an expression of the desired effect of a programme, service or institution in reducing a health problem or improving an unsatisfactory health situation.
source: A GLOSSARY OF TERMS FOR COMMUNITY HEALTH CARE AND SERVICES FOR OLDER PERSONS. World Health Organization, 2004.