In response to an unknown trigger, the immune system may begin producing antibodies that instead of fighting infections, attack the body's own tissues. Treatment for autoimmune diseases generally focuses on reducing immune system activity.
What's taught in school. Some of the items in standardized achievement tests measure the knowledge or skills that students learn in school. In certain subject areas, such as mathematics, children learn in school most of what they know about a subject.
Standard deviation. In statistics, the standard deviation (SD, also represented by the Greek letter sigma Ï or the Latin letter s) is a measure that is used to quantify the amount of variation or dispersion of a set of data values.