Ask The Wizard #356
Consider the scenario where you draw a card from a standard deck of 52 cards, replacing it each time. What is the anticipated number of draws required to collect all 13 cards from a single suit? Calculation methods should utilize calculus.
If the card is drawn at unpredictable intervals rather than strictly once per time unit, the outcome remains unchanged as long as the average interval adheres to an exponential distribution with a mean of 1.
The expected time until a specific card is drawn averages 52 units. In accordance with the characteristics of the exponential distribution, the likelihood that this card has not been drawn after t units of time can be expressed as exp(-t/52).
At any given t time frame, the chance that a particular card has been drawn at least once can be represented as 1-exp(-t/52).
The probability that all 13 designated cards have been drawn at least once after t time units is mathematically calculated as (1-exp(-t/52))^13.
After t time units, the likelihood that at least one of the 13 specific cards has not been drawn is given by 1-(1-exp(-t/52))^13.
The probability that every suit is missing at least one card after t time units would be represented as (1-(1-exp(-t/52))^13)^4.
Putting this equation into an integral calculator , being careful to set to set the bounds of integration from 0 to infinity, yields 712830140335392780521 / 6621889966337599800 = 107.6475362712258
This inquiry was raised and elaborated upon in my discussion forum at Wizard of Vegas .
In Ask the Wizard column 355 A query was posed regarding the glass bridge scenario from Squid Game. The assumption was that players recalled the locations of the safe steps. My question revolves around what the answer would be if the players had no memory of these locations.
Let me clarify your question by rephrasing it without directly referencing the original dilemma.
In a glass bridge game featuring 16 participants, the structure consists of 18 pairs of glass panels. Within each pair, one panel is durable enough to support a player's weight, while the other is fragile, shattering and leading to a player's demise if stepped on. A player falling through ordinary glass will face fatal consequences.
The players are required to move forward in a specific sequence, taking turns one at a time. Players lack any recollection of the secure panels unless evidently indicated by a broken piece in a pair.
If we consider random selections at each pair of glass panels, what is the average number of players who could potentially cross safely?
Please click the button below to view my response.
The table below illustrates the survival probabilities for each player based on their turn order. The bottom right cell indicates that the expected number of players to survive is approximately 0.23884892.
Memoryless Squid Game Bridge Puzzle
Player Number |
Probability Survival |
---|---|
1 | 0.00000381 |
2 | 0.00000763 |
3 | 0.00001526 |
4 | 0.00003051 |
5 | 0.00006094 |
6 | 0.00011911 |
7 | 0.00023545 |
8 | 0.00046159 |
9 | 0.00089886 |
10 | 0.00175139 |
11 | 0.00345091 |
12 | 0.00693198 |
13 | 0.01418276 |
14 | 0.02923634 |
15 | 0.05993762 |
16 | 0.12152477 |
Total | 0.23884892 |
My approach to solving this problem involved employing a Markov chain, which may be complex and time-consuming to detail.
This inquiry is frequently addressed in my column. Wizard of Vegas .
If I hold pocket kings in Texas Hold 'em and there are four other players, what are the chances that at least one of my opponents has pocket aces?
Among the eight cards dealt to the four opponents, the probability that all four are aces is calculated as combin(46,4)/combin(50,8) which results in 0.000303951.
Subsequently, the probability that none of the four aces are in the same hand is established as 1-2^4*4!*4!/8! = 0.228571429. Therefore, the probability that at least one pair of aces exists among them is calculated as 1 - 0.228571429, yielding 0.771428571.
The likelihood that all four aces are in play and at least one hand holds two of them equals 0.000303951 * 0.771428571, which results in 0.000234477.
In the scenario involving eight cards for the four opponents, the probability of three of them being aces is given by combin(4,3) * combin(46,5)/combin(50,8), yielding 0.010212766.
From that point, the calculation for two aces existing in the same hand results in 4*3*COMBIN(3,2)*5*COMBIN(4,2)/(COMBIN(8,2)*COMBIN(6,2)*COMBIN(4,2)) = 0.428571429.
The probability that three of the aces are drawn and two belong to the same hand is 0.010212766 * 0.428571429, which equals 0.0043769.
For the scenario with eight cards among the four opponents, the probability that two of the cards are aces, expressed as combin(4,2) * combin(46,6)/combin(50,8), is 0.104680851.
The probability that both aces are contained within the same hand is calculated as 1/7, giving 0.142857143.
The chance that two of the aces are accounted for and both belong to a single hand amounts to 0.104680851 * 0.142857143, resulting in 0.014954407.
Summing the probabilities of scenarios where at least one opponent holds two aces yields a final total of 0.000234477 + 0.0043769 + 0.014954407, culminating in an overall probability of 0.019565784.
I came across a promotion on an online betting site where a moneyline wager in the NFL automatically turns into a win if the selected team is ahead by 17 points or more. What is the actual worth of this offer?
With this promotion, a bet that might typically be a loss is transformed into a win if the team selected has a lead of 17 or more points, even if they subsequently lose. A noteworthy instance occurred with the Atlanta Falcons when they were ahead by 25 points at 28 to 3, only to end up losing the game 34 to 28. Super Bowl 51 To analyze this situation, I examined 4,131 games from the NFL seasons spanning from 2000 to 2015. The table presented outlines the largest deficits experienced by the winning teams during their respective games, filtering out the five that concluded with ties.
The row labeled 'Tie' refers to the five games across 16 seasons that ended without a winner, so we should exclude these from our calculations. The '0' row represents the 43.7% of games where the winning team was never behind.
Greatest Deficit Overcome
Deficit | Games | Probability |
---|---|---|
Tie | 5 | 0.000000 |
0 | 1804 | 0.437227 |
1 | 100 | 0.024237 |
2 | 29 | 0.007029 |
3 | 560 | 0.135725 |
4 | 235 | 0.056956 |
5 | 23 | 0.005574 |
6 | 131 | 0.031750 |
7 | 622 | 0.150751 |
8 | 39 | 0.009452 |
9 | 34 | 0.008240 |
10 | 195 | 0.047261 |
11 | 84 | 0.020359 |
12 | 14 | 0.003393 |
13 | 49 | 0.011876 |
14 | 104 | 0.025206 |
15 | 10 | 0.002424 |
16 | 6 | 0.001454 |
17 | 36 | 0.008725 |
18 | 14 | 0.003393 |
19 | 2 | 0.000485 |
20 | 4 | 0.000969 |
21 | 22 | 0.005332 |
22 | 0 | 0.000000 |
23 | 2 | 0.000485 |
24 | 5 | 0.001212 |
25 | 1 | 0.000242 |
26 | 0 | 0.000000 |
27 | 0 | 0.000000 |
28 | 1 | 0.000242 |
Total | 4131 | 1.000000 |
The compiled data indicates that in 87 games, a team that was down by 17 points or more still managed to win. When we consider only the 4,126 games that had a clear outcome (excluding ties), this results in a probability of 2.11%.
Given that these specific occurrences can convert a loss into a win, we can double this probability, yielding a total of 4.22%. The house edge for moneyline bets is approximately on par with spread bets at 4.76%. By subtracting the 4.22% from this, we calculate an impressively low house edge of just 0.54% for this promotion.
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