Parameters: numerical measures (of location, dispersion, shape, association, etc.) computed from N data values from a population

Population: a large group (of people, objects, locations) of interest

Statistics: numerical measures (of location, dispersion, shape, association, etc.) computed from n data values from a sample

Sample: a small group taken from the population to represent it

• Population mean: average/expected value of a population
• Sample mean: average/expected value of a sample
• Sample variance: measures the variability/spread of a sample
• Sample standard deviation (SD):

Functions

summary(data)

• yields the mean, quartiles, min, max, etc.

attach(data)

• pulls out data as their own vectors
• mtcars$mpg only exists in mtcars, but attach(mtcars) creates mpg as a standalone vector

var(data)

• returns the variance of the data set provided

sd(data)

• returns the standard deviation of the data set provided

Variables

Mode: most common value (highest frequency)