5.2

Question 1

What is expected value of a random variable

Answer 1

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

Question 2

What is another name for expected value

Answer 2

mean

Question 3

what is the formula for expected value

Answer 3

E(x) = M = Sum xf(x)

Question 4

What is mean a measure of

Answer 4

central location for the random variable

Question 5

What is variance for a random variable

Answer 5

• is a weighted average of the squared deviations of a random variable from its mean
• the weights are the prob(s)

Question 6

What is the variance of a random variable a measure of

Answer 6

of variability or dispersion

Question 7

What is X-M

Answer 7

= deviation

- measures how far a particular value of the random variable is from the expected value or mean

Question 8

Var or Qsquared

Answer 8

0 the sum of the weighted squared deviations for ALL of the values of the random variable

Question 9

what is the definition of the Standard deviation?

What units is it measured in?

Answer 9

the positive squared root of the variance

- measured in the same units as the random variable

Question 10

how is the variance measured

Answer 10

• is measured in squared units which makes it more difficult to interpret

Question 11

What is a bivariate distribution

Answer 11

• a prov distribution involving 2 Random variables
• uses the relative frequency method
• often called joint Prob(s)
• use scatter plots

Question 12

What are the bivariate outcomes

Answer 12

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)

Question 13

What is correlation Coefficent

Answer 13

How the data is related

Question 14

What does it mean if you have a Positive Correlation Coefficient

Answer 14

if x increases then y will also increase and vice versa

Question 15

What does it mean if you have a negative Correlation coefficent

Answer 15

If x increase then y decreases and vice versa

Question 16

What does it mean if you have no correlation

Answer 16

then it will = o

- increases the other stays the same

Question 17

when talking about Correlation coefficent, does it imply cuasation

Answer 17

no, could have an underlying cause affecting each one

Question 18

What is the formula to compute covariance

Answer 18

Qxy = [var (x+y) - Var(x) - Var(y)]/2

Question 19

What is the formula for Correlation Coefficent for a population and sample

Answer 19

Pxy = Qxy / QxQy

rxy = sxy / sxsy

Question 20

What are the Measures of Association for bivariate prob distribution

Answer 20

1. Covariance

2. Correlation Coefficent

Question 21

FOr Correlation Coefficent values near 1 =?

Answer 21

strong positive linear relationship

Question 22

For correlation Coefficent values near -1 =?

Answer 22

strong negative linear relationship

Question 23

for correlation coefficent values near 0 =

Answer 23

lack of (or close to 0= weak) linear relationship