1. Stat 321 – Day 15 More famous continuous random variables “All models are wrong; some are useful” -- G.E.P. Box

2. Last Time – Continuous RV Basics Probability density function (pdf), f(x) Allows us to determine the probability of an interval of values through integration  f(x) by itself doesn’t tell us much  P(X=x) = 0 and P(X < x) = P(X < x)  E(X) =  xf(x) dx  F(x) =  x f(t) dt

3. Special property of exponential P(X > 5 | X > 2)  If you have already waited 2 minutes for the bus, what is the probability you will have to wait at least 5 minutes? = P(X > 5)/P(X > 2) = e -5  / e -2  = e -3 = P(X > 3)  The probability of having to wait at least 3 additional minutes is the same as the probability of having to wait at least 3 minutes.  “Memoryless property”

4. Gamma Distribution

5. Weibull distribution

6. Normal distribution

9. Lognormal

10. For Thursday Quiz on HW 4 Lab 5 due Monday HW 5 posted soon…