Introduction to Linear Regression Analysis, 5th Edition
by Douglas C. Montgomery, Elizabeth A. Peck, G. Geoffrey Vining
APPENDIX C
SUPPLEMENTAL TECHNICAL MATERIAL
C.1 Background on Basic Test Statistics
C.2 Background from the Theory of linear Models
C.3 Important Results on SSR and SSRes
C.4 Gauss-Markov Theorem, Var(ε) = σ2I
C.5 Computational Aspects of Multiple Regression
C.6 Result on the Inverse of a Matrix
C.7 Development of the PRESS Statistic
C.9 Outlier Test Based on R-Student
C.10 Independence of Residuals and Fitted Values
C.11 Gauss-Markov Theorem, Var(ε) = V
C.12 Bias in MSRes When the Model Is Underspecified
C.1 BACKGROUND ON BASIC TEST STATISTICS
We indicate that Y is a random variable that follows a normal distribution with mean μ and variance σ2 by
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C.1.1 Central Distributions
- Let Y1, Y2, …, Yn be independent normally distributed random variables with E(Yi) = μi and Var(Yi) = σ2i. Let a1, a2, …, an be known constants. If we define the linear combination of the Yi's by

then

The key point is that linear combinations of normally distributed random variables also follow normal distributions.
- If Y ~ N(μ, σ2), then
Z is called the standard normal random variable.
- Let Z = (Y – μ)/σ. If Y
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