Mean and Standard deviation of a binomial random variable: If X~B(n,p) then E(X)= np and Var (X)= npq. The standard deviation of X is . Ex. A test used to detect a certain disease is positive for the disease in 15% of the people who take the test. If 100 people are selected at random, what is the expected number who will test positive? Standard deviation helps us quantify the variability in sales. Unit 7 Normal Curves A nature preserve that's tracked bird migrations through New England for decades records tons of bird-related data; everything from wingspan measurements to arrival dates provides examples of normal distributions.
A variance or standard deviation of zero indicates that all the values are identical. Variance is the mean of the squares of the deviations (i.e., difference in values from the mean), and the standard deviation is the square root of that variance. Standard deviation is used to identify outliers in the data.