Distributions

random variable

value depends on outcome of random event

sample space

set of values that random variable can take place

discrete variable

can only take certain numerical values

random variable

outcome not known until experiment carried out

probability distribution

describes probability of any outcome in sample space

• as probability mass function

• table

• diagram

discrete uniform distribution

when all probabilities the same

all values equally likely

notation

capital letter for variable e.g. X = no of heads

lower case for particular value e.g. P(X=x)=…

conditions for binomial distribution

X~B(n,p)

• fixed no. of trials, n

• 2 possible outcomes: success or failure

• independent trials

• fixed probability of success

cumulative probability function

P(X≤x)

discrete random variable

• can take certain value, within know set of values

  • outcome not known until carry out experiment

• but know probability of each possible outcome