Statistics 101 lecture outline: Intro to random variables
Statistics 101: Intro to random variables
Administrivia:
Change in schedule: continuous random variables will be on exam
How many red M&M's are in the bag?
model: 1/5 probability of being red
exactly 25 in each bg
X = number of red M&M.
X is a random variable
P(X = 0) = .2*.2*....*.2 = .2
25
P(X = 25) = .8*.8*.8*...*.8 = .8
25
P(X = x) = 25!/(x!(25-x)!) .2
x
.8
(25-x)
Create sample from class data
Mean and variance of red M&Ms?
mean and variance of sample
"quicker" computation of mean and variance of sample
same method for mean and variance of model
Combinations of random variables
X = number red in one bag
Y = number red in 2nd bag
Z = X + Y is a random variable then!
X and Y independent, so calculation is "easy"
Dependent random variables
R = number red in bag
B = number blue
Y = number yellow
G = number green
U = number ugly orange
Z = R + B + Y + G + U
What is the distribution for Z
last updated: $Date: 2006-04-05 17:38:25 -0400 (Wed, 05 Apr 2006) $