Ch 6 Random variables Flashcards
random variable
takes numerical values that describe the outcomes of some chance process
discrete
random variable that means countable
mean of a discrete random variable aka ?
expected value
when finding the expected value, should you round your answer?
No, do not round
variance is aka?
standard deviation squared
continuous random variable X
takes all values in an interval of numbers (is not countable)
when multiplying each value of a random variable by a positive # b, what happens?
measures of spread & center is multiplied by b
shape of distribution does NOT change
multiplying random variable by constant b multiplies the variance by b^2
when adding each value of a random variable by the same positive # a what happens?
measures of center is added by a
shape and spread doesnt change
mean of difference =
mean of the sum =
difference of the means
sum of the means
variance of the sum =
variance of the difference =
sum of the variances
sum of the variances
what needs to be true to add the variances
the random variables must be independent
never subtract variances, only add-> never add standard deviations
4 requirements for binomial distribution
each observation = 2 categories success or fail
fixed number n of observations
n observations are all independent
probability of success, call it p, is the same for each observation (BINS)
2 types of probability distributions for discrete random variables
geometric or binomial
binomialpdf
probability distribution function for exactly with fixed number trials p(x=___)
binomcdf
cumulative distribution function for inequality w/ fixed number of trials P(x>__)
