Prologue to Discrete Probability

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Prologue to Discrete Probability Epp, area 6. x CS 202 Aaron Bloomfield

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Terminology Experiment A repeatable system that yields one of a given arrangement of results Rolling a pass on, for instance Sample space The scope of results workable For a kick the bucket, that would be qualities 1 to 6 Event One of the example results that happened If you rolled a 4 on the bite the dust, the occasion is the 4

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Probability definition The likelihood of an occasion happening is: Where E is the arrangement of wanted occasions (results) Where S is the arrangement of every single conceivable occasion (results) Note that 0 ≤ |E| ≤ |S| Thus, the likelihood will dependably somewhere around 0 and 1 An occasion that will never happen has likelihood 0 An occasion that will dependably happen has likelihood 1

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Probability is dependably an esteem somewhere around 0 and 1 Something with a likelihood of 0 will never happen Something with a likelihood of 1 will dependably happen You can't have a likelihood outside this range! Take note of that when some person says it has a "100% likelihood) That implies it has a likelihood of 1

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Dice likelihood What is the likelihood of getting "snake-eyes" (two 1's) on two six-sided dice? Likelihood of getting a 1 on a 6-sided kick the bucket is 1/6 Via item administer, likelihood of getting two 1's is the likelihood of getting a 1 AND the likelihood of getting a moment 1 Thus, it's 1/6 * 1/6 = 1/36 What is the likelihood of taking care of business two dice? There are six blends that can yield 7: (1,6), (2,5), (3,4), (4,3), (5,2), (6,1) Thus, |E| = 6, |S| = 36, P(E) = 6/36 = 1/6

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Poker

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The round of poker You are given 5 cards (this is 5-card stud poker) The objective is to get the best hand you can The conceivable poker hands are (in expanding request): No match One sets (two cards of a similar face) Two sets (two arrangements of two cards of a similar face) Three of a kind (three cards of a similar face) Straight (each of the five cards successively – ace is either high or low) Flush (every one of the five cards of a similar suit) Full house (a three of a sort of one face and a couple of another face) Four of a kind (four cards of a similar face) Straight flush (both a straight and a flush) Royal flush (a straight flush that is 10, J, K, Q, A)

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Poker likelihood: illustrious flush What is the possibility of getting an imperial flush? That is the cards 10, J, Q, K, and An of a similar suit There are just 4 conceivable imperial flushes Possibilities for 5 cards: C(52,5) = 2,598,960 Probability = 4/2,598,960 = 0.0000015 Or around 1 in 650,000

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Poker likelihood: four of a kind What is the shot of getting 4 of a kind when managed 5 cards? Conceivable outcomes for 5 cards: C(52,5) = 2,598,960 Possible hands that have four of a kind: There are 13 conceivable four of a kind hands The fifth card can be any of the rest of the 48 cards Thus, add up to potential outcomes is 13*48 = 624 Probability = 624/2,598,960 = 0.00024 Or 1 in 4165

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Poker likelihood: flush What is the shot of getting a flush? That is each of the 5 cards of a similar suit We should do ALL of the accompanying: Pick the suit for the flush: C(4,1) Pick the 5 cards in that suit: C(13,5) As we should do these, we increase the qualities out (by means of the item manage) This yields Possibilities for 5 cards: C(52,5) = 2,598,960 Probability = 5148/2,598,960 = 0.00198 Or around 1 in 505 Note that on the off chance that you don't check straight flushes (and consequently regal flushes) as a "flush", then the number is truly 5108

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Poker likelihood: full house What is the shot of getting a full house? That is three cards of one face and two of another face We should do ALL of the accompanying: Pick the face for the three of a kind: C(13,1) Pick the 3 of the 4 cards to be utilized: C(4,3) Pick the face for the match: C(12,1) Pick the 2 of the 4 cards of the combine: C(4,2) As we should do these, we duplicate the qualities out (by means of the item administer) This yields Possibilities for 5 cards: C(52,5) = 2,598,960 Probability = 3744/2,598,960 = 0.00144 Or around 1 in 694

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Inclusion-prohibition standard The conceivable poker hands are (in expanding request): Nothing One pair cannot incorporate two sets, three of a kind, four of a kind, or full house Two pair cannot incorporate three of a kind, four of a kind, or full house Three of a kind cannot incorporate four of a kind or full house Straight cannot incorporate straight flush or imperial flush Flush cannot incorporate straight flush or regal flush Full house Four of a kind Straight flush cannot incorporate regal flush Royal flush

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Poker likelihood: three of a kind What is the shot of getting a three of a kind? That is three cards of one face Ca exclude a full house or four of a kind We should do ALL of the accompanying: Pick the face for the three of a kind: C(13,1) Pick the 3 of the 4 cards to be utilized: C(4,3) Pick the two other cards' face values: C(12,2) We can't pick two cards of a similar face! Pick the suits for the two different cards: C(4,1)*C(4,1) As we should do these, we duplicate the qualities out (by means of the item govern) This yields Possibilities for 5 cards: C(52,5) = 2,598,960 Probability = 54,912/2,598,960 = 0.0211 Or around 1 in 47

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Poker hand chances The conceivable poker hands are (in expanding request): Nothing 1,302,540 0.5012 One pair 1,098,240 0.4226 Two pair 123,552 0.0475 Three of a kind 54,912 0.0211 Straight 10,200 0.00392 Flush 5,108 0.00197 Full house 3,744 0.00144 Four of a kind 624 0.000240 Straight flush 36 0.0000139 Royal flush 4 0.00000154

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Back to hypothesis once more

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More on probabilities Let E be an occasion in an example space S . The likelihood of the supplement of E is: Recall the likelihood for getting an imperial flush is 0.0000015 The likelihood of not getting a regal flush is 1-0.0000015 or 0.9999985 Recall the likelihood for getting a four of a kind is 0.00024 The likelihood of not getting a four of a kind is 1-0.00024 or 0.99976

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Probability of the union of two occasions Let E 1 and E 2 be occasions in test space S Then p ( E 1 U E 2 ) = p ( E 1 ) + p ( E 2 ) – p ( E 1 ∩ E 2 ) Consider a Venn outline shoot board

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Probability of the union of two occasions p ( E 1 U E 2) S E 1 E 2

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Probability of the union of two occasions If you pick a number somewhere around 1 and 100, what is the likelihood that it is detachable by 2 or 5 or both? Give n a chance to be the number picked p (2| n ) = 50/100 (all the even numbers) p (5| n ) = 20/100 p (2| n ) and p (5| n ) = p (10| n ) = 10/100 p (2| n ) or p (5| n ) = p (2| n ) + p (5| n ) - p (10| n ) = 50/100 + 20/100 – 10/100 = 3/5

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When is betting justified, despite all the trouble? This is a factual examination, not a good/moral discourse What on the off chance that you bet $1, and have a ½ likelihood to win $10? On the off chance that you play 100 times, you will win (by and large) 50 of those times Each play costs $1, every win yields $10 For $100 spent, you win (all things considered) $500 Average win is $5 (or $10 * ½) per play for each $1 spent What on the off chance that you bet $1 and have a 1/100 likelihood to win $10? On the off chance that you play 100 times, you will win (overall) 1 of those times Each play costs $1, every win yields $10 For $100 spent, you win (by and large) $10 Average win is $0.10 (or $10 * 1/100) for each $1 burned through One approach to figure out whether betting is justified, despite all the trouble: likelihood of winning * payout ≥ sum spent Or p(winning) * payout ≥ venture obviously, this is a factual measure

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When is lotto justified, despite all the trouble? Numerous more seasoned lotto amusements you need to pick 6 numbers from 1 to 48 Total conceivable decisions is C(48,6) = 12,271,512 Total conceivable winning numbers is C(6,6) = 1 Probability of winning is 0.0000000814 Or 1 in 12.3 million If you contribute $1 per ticket, it is just measurably justified, despite all the trouble if the payout is > $12.3 million As, on the "normal" you will just profit that method for course, "normal" will require trillions of lotto plays…

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Powerball lottery Modern powerball lottery is somewhat extraordinary Source: http://en.wikipedia.org/wiki/Powerball You pick 5 numbers from 1-55 Total potential outcomes: C(55,5) = 3,478,761 You then pick one number from 1-42 (the powerball) Total conceivable outcomes: C(42,1) = 42 By the item lead, you have to do both So the aggregate conceivable outcomes is 3,478,761* 42 = 146,107,962 While there are numerous "sub" prizes, the likelihood for the big stake is around 1 in 146 million You will "earn back the original investment" if the bonanza is $146M Thus, one ought to just play if the big stake is more noteworthy than $146M If you check in alternate prizes, then you will "make back the initial investment" if the big stake is $121M

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Blackjack

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Blackjack You are at first managed two cards 10, J, Q and K all consider 10 Ace is EITHER 1 or 11 (player's decision) You can select to get more cards (a "hit") You need to get as near 21 as you can If you go over, you lose (a "bust") You play against the house If the house has a higher score than you, then you lose

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Blackjack table

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Blackjack probabilities Getting 21 on the initial two cards is known as a blackjack Or a "characteristic 21" Assume there is just 1 deck of cards Possible blackjack hands: First card is an A, moment card is a 10, J, Q, or K 4/52 for Ace, 16/51 for the ten card = (4*16)/(52*51) = 0.0241 (or around 1 in 41) First card is a 10, J, Q, or K; second card is an A 16/52 for the ten card, 4/51 for Ace = (16*4)/(52*51) = 0.0241 (or around 1 in 41) Total shot of getting a blackjack is the total of the two: p = 0.0483, or around 1 in 21 How fitting! All the more particularly, it's 1 in 20.72 (0.048)

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Blackjack probabilities Another approach to get 20.72 There are C(52,2) = 1,326 conceivable starting blackjack hands Possible blackjack hands: Pick your Ace: C(4,1) Pick your 10 card: C(16,1) Total potential outcomes is the result of the two (64) Probability is 64/1,326 = 1 in 20.72 (0.048)

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Black

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