chpt 15 review

Question 1

What is multiple linear regression used for

Answer 1

more than 2 i.v

Question 2

the variance of the error term E is assumed to be what

Answer 2

the same for all i.v

Question 3

Values of E are

Answer 3

1. independent of each other

2. E is assumed to be normally distributed

Question 4

What is the dependent variable called in the multiple linear regression

Answer 4

the response variable

Question 5

what is the graph called in multiple linear regression

Answer 5

the response surface

Question 6

What does MSE provide in multiple linear regression

Answer 6

provides an unbiased estimate of Q2 (variance of the error term)

Question 7

What is the null hypothesis for the MSE in multiple linear regression

Answer 7

Ho: B1=B2=Bp= 0

MSE s/b close to 1

If Ho: B1=B2=Bp=0 is false, then MSR overstates Q2

MSR/MSE becomes larger

Question 8

What is the adjusted R2 (or adjusted coefficient of determination)?

Answer 8

used for more than one I.V.
r2 always increases as more variables are added

• used to avoid overestimating r2

Question 9

what is the formula for R2 adjusted

Answer 9

see sheet

Question 10

what tests can we use for testing significance in Multiple linear regression?

Answer 10

T-test and the F-test

Question 11

what is the T- test used for in multiple linear regression

Answer 11

test for INDIVIDUAL significance

- separate test is used for I.V.

Question 12

What is the Null and alternative hypothesis for t-test in multiple linear regression

Answer 12

Ho: Bi = 0
Ha: Bi does not equal 0

Question 13

If we reject Ho in the t-test for multiple linear regression, what can we say

Answer 13

that xi is significant

Question 14

What is the degrees of freedom for the t test in multiple linear regression

Answer 14

same as SSE df - n-p-1

p- represents =

Question 15

What is the F test used for in Multiple linear regression

Answer 15

used to test the OVERALL significance of the model

Question 16

What is the null hypothesis for the F- test in multiple linear regression

Answer 16

Ho: B1=B2=Bp=0
Ha: one or more of the parameters is not equal to 0

Question 17

What can you say if you reject Ho in an F test for multiple linear regression

Answer 17

conclude 1 or more than one of the parameters is not = 0

- overall relationship b/w x and y is significant

Question 18

If we do not reject Ho in the F-test for multiple linear regression, what can be said

Answer 18

we do not have sufficient evidence to conclude a significant relationship is present

Question 19

If the F- test in Multiple regression shows overall significance what can we do

Answer 19

a t-test on individual B1 to determine if B1 = 0

if we cannot reject Ho what can this mean?
- could be that w x2 already in the model, x 1 does not make a significant contribution to determining the value of y

Question 20

What is multicollinearity

Answer 20

correlation among the individual variables

Question 21

What can you do to try to avoid multicolinearity

Answer 21

try to not include i.v. s that are highly correlated to each other. in practice this is rarely possible

Question 22

What is the Rule of thumb for Rxy in Multicollinearity

Answer 22

• greater than +.7 or less than -.7 for 2 i.v., this is a Warning sing of potential problems