1. Welcome to .
Week 06 Tues .
MAT135 Statistics

2. Probability
Probability - likelihood of a favorable outcome

3. Probability is defined to be:
# favorable outcomes
total # of outcomes
Usually probabilities are given
in %
P =

4. Probability
This assumes each outcome is equally likely to occur – RANDOM

5. What is P(head on 1 toss of a fair coin)
Probability
IN-CLASS PROBLEM 1
What is P(head on 1 toss of a fair coin)

6. P(head on 1 toss of a fair coin) What are all of the outcomes?
Probability
IN-CLASS PROBLEM 1
P(head on 1 toss of a fair coin) What are all of the outcomes?

7. What are the favorable outcomes?
Probability
IN-CLASS PROBLEM 1
P(head on 1 toss of a fair coin)
What are all of the outcomes?
H or T
What are the favorable outcomes?

8. Probability
IN-CLASS PROBLEM 1
P(head on 1 toss of a fair coin) What are the favorable outcomes? H or T

9. So: P(head on 1 toss of a fair coin) = 1/2 or 50%
Probability
IN-CLASS PROBLEM 1
So: P(head on 1 toss of a fair coin) = 1/2 or 50%

10. Probability The Law of Averages
And why it doesn’t work the way people think it does

11. Probability
IN-CLASS PROBLEM 2
Amy Bob Carlos Dawn Ed ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE What is the probability that Bob will be going to the conference?

12. Probability
IN-CLASS PROBLEM 2
ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE How many outcomes total? How many outcomes favorable?

13. Probability
IN-CLASS PROBLEM 2
ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE How many outcomes total? 10 How many outcomes favorable? 6 have a “B” in them

14. Probability
IN-CLASS PROBLEM 2
ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE So there is a 6/10 or 60% probability Bob will be going to the conference

15. Probability
Because the # favorable outcomes is always less than the total # of outcomes
0 ≤ P ≤ 1 or
0% ≤ P ≤ 100%

16. Probability
And P(all possible outcomes) = 100%

17. Probability
The complement of an outcome is all outcomes that are not favorable Called P (pronounced “P prime") P = 1 – P or P = 100% – P

18. Probability
IN-CLASS PROBLEM 3
To find: P (not 1 on one roll of a fair die) This is the complement of: P (a 1 on one roll of a fair die) = 1/6

19. Probability
IN-CLASS PROBLEM 3
Since: P (a 1 on one roll of a fair die) = 1/6 Then P (not 1 on one roll of a fair die) would be: P = 1 – P = 1 – 1/6 = 5/6

20. Probability
Mutually exclusive outcomes – if one occurs, then the other cannot occur
Ex: if you have a “H” then you can’t have a “T”

21. Probability
Addition rule - if you have mutually exclusive outcomes: P(both) = P(first) + P(second)

22. Probability
Mutually exclusive events: Event A: I am 5’ 2” tall today Event B: I am 5’ 6” tall today

23. Probability The probability that a subscriber uses 1-20 min:
For tables of data, calculating probabilities is easy:
The probability that a subscriber uses 1-20 min:
P(1-20) = 0.17
Minutes Internet Usage
Probability of Being in Category
1-20
9/52 = 0.17 = 17%
21-40
18/52 = 0.35 = 35%
41-60
15/52 = 0.29 = 29%
61-80
0.15 = 15%
81-100
0.02 = 2%
0.00 = 0%
121+

24. Probability
IN-CLASS PROBLEM 4
What is the probability of living more than 12 years after this diagnosis?
Years After
Diagnosis
% of Deaths
1-2 15
3-4 35
5-6 16
7-8 9
9-10 6
11-12 4
13-14 2
15+ 13

25. Probability
IN-CLASS PROBLEM 4
Since you can’t live BOTH AND 15+ years after diagnosis (you fall into one category or the other) the events are mutually exclusive
Years After
Diagnosis
% of Deaths
1-2 15
3-4 35
5-6 16
7-8 9
9-10 6
11-12 4
13-14 2
15+ 13

26. Probability
IN-CLASS PROBLEM 4
You can use the addition rule! P(living >12 years) = P(living13-14) + P(living 15+) = 2% + 13% = 15%
Years After
Diagnosis
% of Deaths
1-2 15
3-4 35
5-6 16
7-8 9
9-10 6
11-12 4
13-14 2
15+ 13

27. Probability
If two categories are “mutually exclusive” you add their probabilities to get the probability of one OR the other

28. Probability
Sequential outcomes – one after the other first toss: H second toss: T third toss: T . . .

29. Probability
Because one outcome in the sequence does not affect the outcome of the next event in the sequence we call them “independent outcomes”

30. Probability
Multiplication rule - if you have independent outcomes: P(one then another) = P(one) * P(another)

31. Probability
To get the probability of both event A AND event B occurring, you multiply their probabilities to get the probability of both

32. What if you had data: Natural Hair Color Eye Color Blonde 34.0% Blue
Probability
IN-CLASS PROBLEM 5
What if you had data:
Natural Hair Color
Eye Color
Blonde
34.0%
Blue
36.0%
Brown
43.0%
64.0%
Red
7.0%
Black
14.0%

33. Probability
IN-CLASS PROBLEM 5
If hair color and eye color are independent events, then find: P(blonde AND blue eyes)
Natural Hair Color
Eye Color
Blonde
34.0%
Blue
36.0%
Brown
43.0%
64.0%
Red
7.0%
Black
14.0%

34. P(blonde AND blue eyes) = =.34 x .36 ≈ .12 or 12%
Probability
IN-CLASS PROBLEM 5
P(blonde AND blue eyes) = =.34 x .36 ≈ .12 or 12%
Natural Hair Color
Eye Color
Blonde
34.0%
Blue
36.0%
Brown
43.0%
64.0%
Red
7.0%
Black
14.0%

35. What would be the probability of a subscriber being both
(1-20 minutes)
and
(61-80 minutes)?
Minutes Internet Usage
Probability of Being in Category
1-20
9/52 = 0.17 = 17%
21-40
18/52 = 0.35 = 35%
41-60
15/52 = 0.29 = 29%
61-80
0.15 = 15%
81-100
0.02 = 2%
0.00 = 0%
121+

36. They are mutually exclusive categories
Probability
Zero!
They are mutually exclusive categories

37. Questions?

38. Probability # favorable outcomes If P = total # of outcomes
you’ll need to know the total
# of outcomes!
If P =

39. Fundamental Counting Principle
the number of ways things can occur

40. COUNTING
IN-CLASS PROBLEM 6
Male/Female and Tall/Short How many ways can these characteristics combine?

41. Male/Female and Tall/Short I try to build a tree:
COUNTING
IN-CLASS PROBLEM 6
Male/Female and Tall/Short I try to build a tree:

42. Male/Female and Tall/Short Male Female / \ / \ Tall Short Tall Short
COUNTING
IN-CLASS PROBLEM 6
Male/Female and Tall/Short Male Female / \ / \ Tall Short Tall Short

43. COUNTING
IN-CLASS PROBLEM 6
Male Female / \ / \ Tall Short Tall Short 4 possible ways to combine the characteristics: MT MS FT FS

44. COUNTING
IN-CLASS PROBLEM 7
How about: Blonde/Brunette/Redhead and Blue eyes/Green eyes/Brown eyes Build a tree!

45. COUNTING
IN-CLASS PROBLEM 7
Blonde Brunette Red / | \ / | \ / | \ Bl Br Gr Bl Br Gr Bl Br Gr How many ways to combine these characteristics?

46. COUNTING
IN-CLASS PROBLEM 7
Blonde Brunette Red / | \ / | \ / | \ Bl Br Gr Bl Br Gr Bl Br Gr How many ways to combine these characteristics? 9: BdBl BdBr BdGr BtBl BtBr BtGr RdBl RdBr RdGr

47. Fundamental Counting Principle
The number of ways in which characteristics can be combined is found by multiplying the possibilities of each characteristic together

48. COUNTING
IN-CLASS PROBLEM 8
Two pairs of jeans: black blue Three shirts: white yellow blue Two pairs of shoes: black brown How many different ways can you get dressed?

49. COUNTING
IN-CLASS PROBLEM 8
Two pairs of jeans: black blue Three shirts: white yellow blue Two pairs of shoes: black brown How many different ways can you get dressed? 2 * 3 * 2 = 12

50. COUNTING
IN-CLASS PROBLEM 9
Multiple choice quiz 10 questions 4 choices on each How many ways are there to answer the questions on the test?

51. Multiple choice quiz 10 questions 4 choices on each
COUNTING
IN-CLASS PROBLEM 9
Multiple choice quiz
10 questions
4 choices on each
4 * 4 * 4 *… (10 of them)

52. Multiple choice quiz 10 questions 4 choices on each
COUNTING
IN-CLASS PROBLEM 9
Multiple choice quiz
10 questions
4 choices on each
4 * 4 * 4 *… (10 of them)
Otherwise known as 410
= 1,048,576

53. How many ways out of the 1,048,576 can you get a 100?
COUNTING
IN-CLASS PROBLEM 10
Multiple choice quiz
10 questions
4 choices on each
How many ways out of the 1,048,576 can you get a 100?

54. 1/1,048,576 chance of getting 100% if you guess on all questions
COUNTING
IN-CLASS PROBLEM 10
Multiple choice quiz
10 questions
4 choices on each
1/1,048,576 chance of getting 100% if you guess on all questions

55. How many zip codes? 5 slots Can’t start with a 0 or a 1 COUNTING
IN-CLASS PROBLEM 11
How many zip codes?
5 slots
Can’t start with a 0 or a 1

56. COUNTING
IN-CLASS PROBLEM 11
How many area codes?
___ ___ ___ ___ ___

57. COUNTING
IN-CLASS PROBLEM 11
How many area codes?

58. How many area codes? 8 10 10 10 10 8*104 = 80,000 COUNTING
IN-CLASS PROBLEM 11
How many area codes?
8*104 = 80,000

59. In Canada, they alternate Letter Number Letter Number Letter Number
COUNTING
IN-CLASS PROBLEM 12
In Canada, they alternate Letter Number Letter
Number Letter Number
How many area codes can they have?

60. In Canada, they alternate Letter Number Letter Number Letter Number
COUNTING
IN-CLASS PROBLEM 12
In Canada, they alternate Letter Number Letter
Number Letter Number
26*10*26 * 10*26*10
= 263 * 103 = 17,576,000
(A whole lot more than 80,000!)

61. Questions?

62. Combinatorics
The number of ways in which characteristics can be combined is found by multiplying the possibilities of each characteristic together

63. Combinatorics
Combinatorics expands on this idea – from a complete group, how many subgroups can you select?

64. Combinatorics
IN-CLASS PROBLEM 13
If you have 5 club members, how many ways can you pick 3 of them to go to a conference? Amy Bob Carlos Dawn Ed

65. Combinatorics
IN-CLASS PROBLEM 13
If you have 5 club members, how many ways can you pick 3 of them to go to a conference? Amy Bob Carlos Dawn Ed The order in which they are selected is not important

66. You can make a list: ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE
Combinatorics
IN-CLASS PROBLEM 13
You can make a list: ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE

67. Combinatorics
Even for a small list, it’s a lot of work And… how do you know you’ve got them all?

68. Combinatorics
This is called “combinations” The formula: n! r!(n−r)! In the book: n r Read it as “n pick r” On a calculator: nCr

69. Combinatorics
Combinations an ordered arrangement of items such that: the items are selected from the same group no item is used more than once the order makes no difference

70. Combinatorics
For nCr or n!/r!(n-r)! “n” is the total number in the group “r” is the number you are selecting

71. Combinatorics
IN-CLASS PROBLEM 13
If you have 5 club members, how many ways can you pick 3 of them to go to a conference? Amy Bob Carlos Dawn Ed What is “n”? What is “r”?

72. Combinatorics
IN-CLASS PROBLEM 13
If you have 5 club members, how many ways can you pick 3 of them to go to a conference? Amy Bob Carlos Dawn Ed n=5 r=3 Calculate n! r!(n−r)!

73. Combinatorics
IN-CLASS PROBLEM 13
If you have 5 club members, how many ways can you pick 3 of them to go to a conference? n=5 r=3 n! r!(n−r)! = 5! 3!(5−3)! = 5! 3!2! = 5x4x3x2x1 (3x2x1)(2x1) = 10

74. Did we have 10 listed before? ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE
Combinatorics
IN-CLASS PROBLEM 13
Did we have 10 listed before? ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE

75. Combinatorics
IN-CLASS PROBLEM 13
Try this on your calculator! Look for nCr Usually you enter: 5 nCr 3 Do you get 10?

76. Combinatorics
IN-CLASS PROBLEM 14-16
Try: 8C C C10

77. Combinatorics
What happens if order IS important in selecting your subgroup?

78. Combinatorics
IN-CLASS PROBLEM 17
If you have 5 club members, how many ways can you pick a President, VP and Treasurer?
Amy Bob Carlos Dawn Ed

79. Combinatorics
Example: P: A VP: B or C or D or E T: whichever you didn’t pick for VP

80. Combinatorics
This is going to be a REALLY hard one to do by making a list!

81. And that’s just with Amy as president!VP
Treas A B C D E
And that’s just with Amy as president!

82. Combinatorics
We call this “permutations” an ordered arrangement of items such that: no item is used more than once the order DOES make a difference

83. Combinatorics
# of permutations of n things taken r at a time: n P r = n! (n−r)!

84. For our club members: 5P3 = 5! (5−3)! = 5x4x3x2x1 2x1 = 60
Combinatorics
IN-CLASS PROBLEMS 17
For our club members: 5P3 = 5! (5−3)! = 5x4x3x2x1 2x1 = 60

85. Combinatorics
IN-CLASS PROBLEMS 18-20
Try: 8P5 4P0 12P10

86. Combinatorics
Word problems: Try to figure out if order is important or not Usually, it’s not, so it’s combinations If it is, it’s permutations

87. Questions?

88. You survived!
Turn in your homework! Don’t forget your homework due next class! See you Thursday!