Exam 4 Study Questions
If a categorial indepenent variable contains two categories, then ____ dummy variables will be needed to uniquely represent these categories
1
If SSR = 36 and SSE =4, determine SST and then compute the coefficient of determination, r^2, and interpret the meaning
36 + 4 = 40 r^2 = .90 X .9 100% = 90% of the variation in the dependent variable can be explained by the independent variable
How do you interpret a coefficient of determination, r^2, equal to .80
80% of the variation in the dependent variable can be can be explained by the variation of the independent variable
MSR/MSE =
F stat
Y = 10 +5X +3X Interpret the meaning of the slopes Interpret the meaning of the Y intercept
If X2 is constant when X1 increases one unit, Y increases 5 units THe Y intercept 10 is the estimate of the mean value if X1 and X2 are both 0
Regression = ___ and is also SS_
K and SSR
The F statistic for testing the entire regression model can be expressed as:
MSR/MSE
SSE IS
RESIDUAL
If SSR = 120, why is it impossible for SST to equal 110
SInce SST = SSR + SSE cannot be a negative number, SST must be at least as large as SSR
SSR IS
SS REGRESSION
How do you find MSE
SSE/n-k-1
MSR =
SSR/K
In order to calculate the coefficient of multiple determination r^2, you would use which of the following formulas
SSR/SST
To test for the significance of individual regression coefficients in a multiple regression model with more than 2 explanatory variables, you would use an
T test
y = 2+5x whats the meaning of the y intercept bo Whats the meaning of the slope b1 Predict the value of y for x =3
When X=0, the estimated expected value of y is 2 For each increase in the value of X by 1 unit, you can expect an increase by an estimated 5 units 2+5(3) = 17
Fitting a straight line to a set of data yields the following prediction line: Y = 16- 0.5x Interpret the meaning of Y intercept b0 interpret the meaning of the slope b1 predict the value of y for x =6
When x = o the estimated expected value of y is 16 for each increase in the value by 1 unit, you can expect a decrease of 0.5 16-.5(6) = 13
A microeconomist wants to determine how corporate sales are influenced by capital and wage spending by companies. She proceeds to randomly select 26 large corporations and record information in millions of dollars. A statistical analyst discovers that capital spending by corporations has a significant inverse relationship with wage spending. What should the microeconomist who developed this multiple regression model be particularly concerned with?
collinearity
When two or more of the explanatory variables are highly correlated, this situation is referred to as
collinearity
THe variance inflationary factor measures the
correlation of x variables with each other
which of the following is not used to find a best model
durbin
In a multiple regression model, which of the following is correct regarding the value of the adjusted r^2
it can be negative
The Coefficient of multiple determination r^2
measures the proportion of variation in Y that is explained by X1 AND X2
The total is
n-1
How do you find the error
n-k-1
How many degrees of freedom are associated with the multiple regression model when running a t test for the individual coefficients
n-k-1
If the values of X in problem 13.1 range from 2 to 25, should you use this model to predict the mean value of Y when X equals a. 3 b. -3 c. 0 d. 24
only 3 and 24 because they are in range
If p < a
reject and appears
Which of the following is not a residual plot that is typically used in multiple regression analysis
residuals vs correlation coefficients
If p < a then its
statistically significant
in multiple regression, the ______ procedure permits variables to enter and leave the model at diff stages of its development
stepwise
In a multiple regression problem involving two independent variables, if b1 is computed to be 2.0, it means that
the estimated value of Y increases by an avg 2 units for each increase of 1 unit of x, holding x2 constant
thE ADJ R^2 IS ADJUSTED FOR THE:
the number of predictors and the sample size
An interaction term in an multiple regression model may be used when
the relationship between x1 and y changes for differing values of X2
A dummy variable is used as an independent variable in a regression model when
the variable involved is categorical
A regression diagnostic tool used to study the possible effects of collinearity is
the variance inflationary factor
The curvilinear model is one that contains which of the following x terms
x^2