Chapter 7: Multivariate Regression

Question 1

How to think when multiplying two matrices according to the dot product?

Answer 1

Each row times each column (corresponding order). Sum all multiplications for each procedure.

Question 2

How to take the inverse of a (2x2) matrix? Describe the procedure using X = [a b, c d]

Answer 2

X^(-1) = 1/det(X) [d -b, -c a] = 1/(ad-bc) [d -b, -c a]