The standard deviation is a measure of how the data is clustered about the mean. For large sets of data, approximately 68.3% of the data lies within one standard deviation of the mean and approximately 95.4% of the data lies within two standard deviations of the mean.
Influenza (also known as the flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccination each year.
Influenza (Flu) The flu is an infectious disease that causes symptoms such as fever, cough, sore throat, headache, muscle aches, and chills. The annual flu vaccine can prevent most of the circulating influenza strains. Read about flu symptoms, and learn more about the flu shotÂ».