exam issues Flashcards
What is the relationship between t test and f test?
f test is the square of a t test.
What is the coefficient of determination?
R^2
How do you estimate the slope coefficient using OLS
ybar - b1bar(xbar) must be using the means!
What is the OLS estimate of B0 if it is just a B0 in the model?
It is just ybar
How would I calculate R^2 from data?
You do TSS which is sum of (yi-ybar)
Then work out ESS (ybar hat - ybar)^2
What is the coefficient of determination?
R^2
yi-ybar and square all these
What is an alternative way to work out SE of regression?
sqrt RSS/DOF
How do you get R^2 from correlation coefficient?
r^2 = R^2
What does it mean that the expectation of the error term of 0
What does the constant variance mean?
On average the error terms are equaled to 0
-does not mean that small x has a different level of uncertainty compared to big x
If OLS assumptions are satisfied what do the estimates?
Estimates have smallest variance and are unbiased.
What assumption is needed.
When does TSS change?
When dependent variable changes
What is a unit change in a %?
A % point change
What is the t-ratio?
What does it tell us?
Coefficient divided by the standard error
The closer to 2, the more significant.
What is the standard error of the regression?
You can get it from MS which is the error of the error term.
Then take the square root.
What is the RMSE?
Root mean squared error
sqaure root of MS of residuals
What are the ways that d can be interpreted?
a) the equality signs in beta
b) the difference in parameter between restircred and unrestricted model
When you are testing that all slope coefficients are equal to 0 what is the RSSR?
Just the TSS of the unrestricted model
For a single restriction what is the relationship between f test and t test?
f test is square of t test
What is the F test trying to say?
That the model explains some of the variatino
What is a pvalue?
Proability of observing a test statistic given H0 is true
Graphically what is the power of a test?
-The proportion of the given region which is in the rejection region.
