Questions about concepts Exam 3

Question 1

What are residuals?

Answer 1

Difference between the actual value vs the predicted value

Question 2

What is the line of best fit?

Answer 2

a straight line drawn on a scatter plot that best represents the trend of the data points

Question 3

What is the method of least squares?

Answer 3

It is a process that finds the line of best fit that minimizes the sum of residuals

Question 4

In a sample linear correlation, what are the range of values?

Answer 4

-1 and +1

Question 5

What is a sample linear correlation?

Answer 5

It is a concept that measures the strength and direction of a linear relationship between two variables in a sample dataset

Question 6

In a multiple regression model what is the probability distribution of the error?

Answer 6

0

Question 7

What is the standard deviation of a multiple regression model assumed to be?

Answer 7

constant for all values of the independent variables

Question 8

What are the values of the errors? Independent or dependent?

Answer 8

Independent

Question 9

How do you test the vailidity of the multiple regression model?

Answer 9

F test

Question 10

What is the null hypothesis involving two independent variables?

Answer 10

B1=B2=0

Question 11

When the independent variables are correlated with one another this is called?

Answer 11

Multicollinearity

Question 12

What does extrapolation refer to?

Answer 12

Estimating the mean value of the dependent variable for values outside the experimental range

Question 13

What is part of the variable screening process?

Answer 13

1. Higher order terms are not considered 2. Common sense should be used when eliminating variables 3. Model building begins after screening

Question 14

What can NOT be used in a high dimensional configuration where the number of samples n is less than the number of predictors?

Answer 14

Backward selection

Question 15

Which model assement should be minimized for the best model

Answer 15

AIC

Question 16

Which model assesment should be maximized

Answer 16

Adujsted R^2

Question 17

What is the method of least squares

Answer 17

finds the line of best fit that minimizes the sum of residuals

Question 18

Leverage is extreme in what? Outlier is extreme in what?

Answer 18

Leverage is extreme in x (independent), outlier is extreme in y (dependent)

Question 19

if the standardized residual is greater than 3 or less than 3 it is considered a what?

Answer 19

Outlier

Question 20

If a correlation coefficient in the matrix is bigger than 0.8 in absolute value what issue is that?

Answer 20

Multicolinearity