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Two fair six-sided dice are tossed independently. Let \(M=\) the maximum of the two tosses (so \(M(1,5)=5, M(3,3)=3\), etc.). a. What is the pmf of \(M\) ? b. Determine the cdf of \(M\) and graph it.

Short Answer

Expert verified
The PMF of \(M\) is given by specific probabilities for each value from 1 to 6. The CDF is a step function that rises discretely as \(m\) increases from 1 to 6.

Step by step solution

01

Determine Possible Outcomes for M

When two six-sided dice are rolled, each die can show an integer value between 1 and 6. The maximum value, \(M\), can take any integer value from 1 to 6 depending on the outcomes of the two dice.
02

Find Probability Mass Function (PMF) of M

Calculate the probability for each possible value of \(M\). For instance, \(M = 1\) only occurs if both dice show 1, which is one outcome out of 36 possible outcomes (probability \(\frac{1}{36}\)). For \(M = 2\), it occurs if (1,2), (2,1), or (2,2) which is 3 outcomes (probability \(\frac{3}{36}\)). This continues similarly for \(M = 3, 4, 5, 6\). The calculated probabilities are: - \(P(M=1) = \frac{1}{36}\) - \(P(M=2) = \frac{3}{36} = \frac{1}{12}\) - \(P(M=3) = \frac{5}{36}\) - \(P(M=4) = \frac{7}{36}\) - \(P(M=5) = \frac{9}{36} = \frac{1}{4}\) - \(P(M=6) = \frac{11}{36}\).
03

Write the PMF of M

The PMF of \(M\) is given as follows:\[P(M=m)= \begin{cases} \frac{1}{36}, & \text{if } m=1 \\frac{1}{12}, & \text{if } m=2 \\frac{5}{36}, & \text{if } m=3 \\frac{7}{36}, & \text{if } m=4 \\frac{1}{4}, & \text{if } m=5 \\frac{11}{36}, & \text{if } m=6 \end{cases}\]
04

Determine Cumulative Distribution Function (CDF) of M

The cumulative probabilities are: - \(P(M \leq 1) = P(M=1) = \frac{1}{36}\) - \(P(M \leq 2) = P(M=1) + P(M=2) = \frac{1}{36} + \frac{1}{12} = \frac{4}{36}\)- \(P(M \leq 3) = \frac{4}{36} + \frac{5}{36} = \frac{9}{36}\)- \(P(M \leq 4) = \frac{9}{36} + \frac{7}{36} = \frac{16}{36}\)- \(P(M \leq 5) = \frac{16}{36} + \frac{1}{4} = \frac{25}{36}\)- \(P(M \leq 6) = \frac{25}{36} + \frac{11}{36} = 1\). Thus, the CDF of \(M\) is:\[F(m) = \begin{cases} 0, & \text{if } m < 1 \\frac{1}{36}, & \text{if } 1 \leq m < 2 \\frac{1}{9}, & \text{if } 2 \leq m < 3 \\frac{1}{4}, & \text{if } 3 \leq m < 4 \\frac{4}{9}, & \text{if } 4 \leq m < 5 \\frac{25}{36}, & \text{if } 5 \leq m < 6 \1, & \text{if } m \geq 6\end{cases}\]
05

Graph the CDF

To graph the CDF of \(M\), plot \(m\) on the x-axis and \(F(m)\) on the y-axis with horizontal lines representing the cumulative probability value at each step. The CDF graph is a step function that rises from 0 to 1, increasing at the points where \(m\) is an integer from 1 to 6.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Cumulative Distribution Function
The Cumulative Distribution Function (CDF) is a fundamental concept in probability theory. It tells us the probability that a random variable will take a value less than or equal to a specific value. In simple terms, it accumulates probabilities from the smallest up to the specific value. The best way to think of it is like a continuous sum. With a CDF, you're basically seeing how much probability you have built up at each point.

For example, in the dice problem, if you want to know the CDF for the random variable representing the maximum of the two dice rolls, say at the value 3, you look at how many ways the maximum can be less than or equal to 3 when two dice are rolled. Calculating this gives you a probability that, as you go through the possible dice values and rise to larger numbers, you collect more and more of this probability until you reach 1.

Graphically, this is shown as a step function where each step represents the accumulated probability as you increase to the next possible maximum value. Importantly, a CDF always starts from 0 and ends at 1, capturing all possible outcomes of the experiment.
Discrete Probability Distribution
A Discrete Probability Distribution is a way to represent the probabilities of all possible values for a discrete random variable. These are variables like the outcomes when you roll a pair of dice. Each possible outcome has a specific probability assigned to it, and altogether, these probabilities help us understand the distribution of outcomes.

In the context of dice, the discrete probability distribution for the maximum of two tossed dice, noted as M, captures how likely each value of M is, from 1 to 6. The Probability Mass Function (PMF) provides this information. It lays out how probable it is for the maximum rolled value to be each number within its range.

Because each die is independent and their outcomes are finite and countable, it falls neatly into the category of a discrete distribution. Discrete probability distributions like this are essential for understanding games of chance, decision making under uncertainty, and even for more complex statistical modeling.
Dice Probability
Dice probability is a classic example of probability theory and a great way to understand some fundamental concepts. When rolling dice, each face of the die has the same chance of showing up; for a six-sided die, that's a probability of 1/6 per face. When rolling two dice, the number of possible outcomes expands to 36, since each die is independent, and their probabilities should be multiplied.

In our scenario, we're interested in the maximum value of the two dice, a slightly more complex problem than simply summing the dice. This involves understanding how different combinations of faces can create these maxima and what their probabilities are. We find the PMF to conclude each probability, as seen for each potential maximum outcome from 1 to 6.
  • For instance, to determine the probability of having a maximum value of 4, you go through combinations like (3,4), (4,3), or (4,4).
  • Dice probability offers a hands-on approach to grasping probabilities and understanding the behavior of discrete events.
Understanding these ideas using dice demonstrates seamless transitions between theory and tangible experiments, helping anchor abstract concepts in everyday activities.

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Most popular questions from this chapter

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