Statistical concepts

Random Variable
A random variable is value which represents some measurable quantity or category associated with an experiment.

variables can be quantitative or categorical continuous or discrete

measures of location
sample mean sample median

measures of dispersion
variance standard deviation interquartile range

Quantitative Discrete Continuous Categorical Discrete Binary Continuous

Summarising quantitative data
measures of average or typical calues

sample mean sample median

"The median of a sample of data with an odd number of values is the middle value of the ordered sample. If the sample size is even, the median is the average of the two middle values. "

Measures of dispersion
standard deviation interquartile range

basic properties of events
P(A and B) = P(A) + P(B) - P(A or B)

given mutually exclusive events A and B

P(A and B) = P(A) + P(B)

Law of Total Probability
P(B) = \sigma {}

Discrete Distributions
probability mass function

the mean of a discrete probability distribution is

E(X) = \sigma_{x*p(x)}