Warm-up 1. A concert hall has 2000 seats. There are 1200 seats on the main floor and 800 in the balcony. 40% of those in the balcony buy a souvenir program. 50% of those on the main floor buy a souvenir program. At a certain performance all seats are occupied. If an audience member is selected at random, what is the probability that a program was purchased? 2. A spinner on a full circle can take on any decimal value between 0 and 400. What is the probability that the spinner will land between 175 and 225?
Continuous Random Variables Density Functions
Continuous Random Variables Possible values contain an entire interval.
Ex: Weight of newborns Nearest pound Nearest tenth of pound
Fit more & more rectangles It approaches a curve as the rectangles become smaller & has greater accuracy.
Density Function Probability distribution for a continuous random variable (f(x)). The graph is a smooth curve called the density curve. F(x) 0 Total area under the curve = 1.
Uniform Distribution All occur in equal distributions
Ex: What’s the area from 4.5 to 5.5?What’s the area from 5.5 to 6?
Discrete:
Continuous: Why? It’s like finding the area of a rectangle with width = 0.
Probabilities for continuous random variables are usually calculated using cumulative areas. P(x<0.5) Found using integrals & calculus – but we’ll use tables!
If we have a uniform continuous function from 3 to 8, find the height.
Ex. Find P(x < 10) Find P(x < 35) minutes
Ex: Find P(x<4) Find P(x<2) 0.25
Ex: Find P(x<20) Find P(x>70) Find P(20<x<70)
Homework P. 365 (20-26)