5.2 Flashcards
What is expected value of a random variable
weighted average of the values of the random variable where the weights are the prob(s)
- does not have to be a value the random variable can assume
What is another name for expected value
mean
what is the formula for expected value
E(x) = M = Sum xf(x)
What is mean a measure of
central location for the random variable
What is variance for a random variable
- is a weighted average of the squared deviations of a random variable from its mean
- the weights are the prob(s)
What is the variance of a random variable a measure of
of variability or dispersion
What is X-M
= deviation
- measures how far a particular value of the random variable is from the expected value or mean
Var or Qsquared
0 the sum of the weighted squared deviations for ALL of the values of the random variable
what is the definition of the Standard deviation?
What units is it measured in?
the positive squared root of the variance
- measured in the same units as the random variable
how is the variance measured
- is measured in squared units which makes it more difficult to interpret
What is a bivariate distribution
- a prov distribution involving 2 Random variables
- uses the relative frequency method
- often called joint Prob(s)
- use scatter plots
What are the bivariate outcomes
can have 2 values either value 1 or value 2
- ex. roll a 2 dice
we are interested in the relationship between the two dice rolled
(2 random variables)
What is correlation Coefficent
How the data is related
What does it mean if you have a Positive Correlation Coefficient
if x increases then y will also increase and vice versa
What does it mean if you have a negative Correlation coefficent
If x increase then y decreases and vice versa
What does it mean if you have no correlation
then it will = o
- increases the other stays the same
when talking about Correlation coefficent, does it imply cuasation
no, could have an underlying cause affecting each one
What is the formula to compute covariance
Qxy = [var (x+y) - Var(x) - Var(y)]/2
What is the formula for Correlation Coefficent for a population and sample
Pxy = Qxy / QxQy
rxy = sxy / sxsy
What are the Measures of Association for bivariate prob distribution
- Covariance
2. Correlation Coefficent
FOr Correlation Coefficent values near 1 =?
strong positive linear relationship
For correlation Coefficent values near -1 =?
strong negative linear relationship
for correlation coefficent values near 0 =
lack of (or close to 0= weak) linear relationship
