MARE 250 Dr. Jason Turner The Normal Distribution
Define Normal
So, am I Normal? Standardized Normal Distribution –
Properties of Normality
% of all possible observation lie w/in 1 std. dev. of the mean μ – σ and μ + σ % of all possible observation lie w/in 2 std. dev. of the mean μ – 2σ and μ + 2σ % of all possible observation lie w/in 3 std. dev. of the mean μ – 3σ and μ + 3σ
Assessing Normality Large samples: Small sample:
Normal Probability Plot: Assessing Normality
Probability Plots - PP
When Using Probability Plots
Guidelines for Probability Plots
Testing for Normality
Normality Tests Anderson-Darling (α=0.10) Ryan-Joiner (Shapiro-Wilk) (α=0.10) Kolmogorov-Smirnov (α=0.15) More powerful
Probability Plots - PP
This is not a Test… Hypothesis testing – Hypothesis – Hypothesis Testing 101