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Dec 27, 2021 at 17:06 comment added user801306 If you compute $P^2$ and sum the third and fourth entries in the first row you'll get the same exact value I obtain in my answer
Dec 27, 2021 at 13:14 comment added user801306 The fourth entry in the first row of $P^j$ indicates the probability you observe five $4$'s after the $j^\text{th}$ roll. You don't have to obtain these five $4$'s in one shot for this to take place.
Dec 27, 2021 at 6:53 comment added CyanCoding How do you know the probability of having at least four 4's is the sum of the third and fourth entries? The fourth entry assumes you get all four matching in one roll. If I understand it correctly, the third entry assumes you get three matching on your first roll. So why is it the sum?
Dec 27, 2021 at 2:58 comment added user801306 FYI learning about Markov chain's is an exciting and surprisingly painless experience. I highly recommend it!
Dec 27, 2021 at 2:54 comment added user801306 So, since $$P^3=\begin{pmatrix}\frac{1953125}{10077696}&\frac{1421875}{3359232}&\frac{1035125}{3359232}&\frac{753571}{10077696}\\ 0&\frac{15625}{46656}&\frac{11375}{23328}&\frac{8281}{46656}\\ 0&0&\frac{125}{216}&\frac{91}{216}\\ 0&0&0&1\end{pmatrix}$$ The probability of getting at least four $4$'s after $3$ rolls is $$\frac{1035125}{3359232}+ \frac{753571}{10077696}\approx 0.38$$
Dec 27, 2021 at 2:54 comment added user801306 Let $X_0=2$ and $X_j$ be the number of fours that appear after $j$ rolls. Then $\{X_j\}_{j\geq 0}$ is a Markov chain with states $\{2,3,4,5\}$ and has state transition matrix $$P=\begin{pmatrix}\frac{125}{216}&\frac{25}{72}&\frac{5}{72}&\frac{1}{216}\\ 0&\frac{25}{36}&\frac{5}{18}&\frac{1}{36}\\ 0&0&\frac{5}{6}&\frac{1}{6}\\ 0&0&0&1\end{pmatrix}$$ The sum of the third and fourth entries in the first row of $P^j$ indicate the probability of having at least four $4$'s after $j$ rolls.
Dec 27, 2021 at 2:49 comment added CyanCoding A little above my math knowledge haha. They're referenced in the Yahtzee probability article (which achieves a similar goal of mine but doesn't show all the equations) so I'll do more research on that topic. Thanks!
Dec 27, 2021 at 2:35 comment added user801306 Are you familiar with Markov Chains?
Dec 27, 2021 at 2:16 comment added CyanCoding I've figured it out, but how does the formula change if I was calculating the chances with three turns left? Wouldn't I have a X, Y, and Z, with Z being the number of fours in my third round? How can I implement that?
Dec 27, 2021 at 0:59 vote accept CyanCoding
Dec 26, 2021 at 18:44 history answered user801306 CC BY-SA 4.0