Stem-and-Leaf plot is a method of organizing numerical data in order of place value. The 'ones digit' and the 'tens digit and greater' of each data item is separated as leaves and stems respectively. The stem-and-leaf plot below shows the number of students enrolled in a dance class in the past 12 years.
Vaccination with live viruses may interfere with TST reactions. For persons scheduled to receive a TST, testing should be done as follows: Either on the same day as vaccination with live-virus vaccine or 4-6 weeks after the administration of the live-virus vaccine. At least one month after smallpox vaccination.
Most people infected with tuberculosis have inactive disease that does not cause any symptoms. In these people, a skin test for tuberculosis (called a PPD skin test, for protein purified derivative) will show positive results within three months of getting the infection. Once a PPD is positive, it usually will remain positive throughout life.