Chapter 5

Basic Concepts of Probability


Terminology

Basic Laws of Probability

P(blue)=.35    P(red)=.45    P(yellow)=.20 
P(red or yellow) = P(red)+ P(yellow) 
= .45+.20
= .65

Example:

P(in office and someone looks)

= P(in office) * P(someone looks)
= .65 x .15
= .0975

Question:

Joint and Conditional Probabilities

An Example: Drinking & Driving

Accident
No Accident
Total
Drinking
7
23
30
Not Drinking
6
64
70
Total
13
87
100
= P(Drinking) x P(Accident)
= 0.30 x 0.13
= 0.0390
= 7/13
= 0.5385
= 7/30
= 0.2333

Factorials!

Permutations

p1, p2, p3 p1, p3, p2 
p2, p1, p3 p2, p3, p1 
p3, p1, p2 p3, p2, p1 

ch5-2
ch5-3
ch5-4

ch5-5
ch5-6
ch5-7

p1, p2 p1, p3 p1, p4 p1, p5 
p2, p1 p2, p3 p2, p4 p2, p5 
p3, p1 p3, p2 p3, p4 p3, p5 
p4, p1 p4, p2 p4, p3 p4, p5 
p5, p1 p5, p2 p5, p3 p5, p4 

Combinations

ch5-8
ch5-9
ch5-10
ch5-11

1&2  1&3  1&4  1&5  2&3 
2&4  2&5  3&4  3&5  4&5 

The Binomial Distribution

ch5-12
ch5-13

Examples:

ch5-15
ch5-16
ch5-17

ch5-18
ch5-19
ch5-20

Plotting Binomial Distributions

Number Heads
Probability
0
.001
1
.010
2
.044
3
.117
4
.205
5
.246
6
.205
7
.117
8
.044
9
.010
10
.001

Number Correct
Probability
0
.001
1
.010
2
.044
3
.117
4
.205
5
.246
6
.205
7
.117
8
.044
9
.010
10
.001