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Pair-a-dice Suppose you roll a pair of fair, six-sided dice. Let \(T=\) the sum of the spots showing on the up-faces. (a) Find the probability distribution of \(T\). (b) Make a histogram of the probability distribution. Describe what you see.

Short Answer

Expert verified
(a) The probability distribution of \( T \) is symmetric around 7, with probabilities ranging from \( \frac{1}{36} \) to \( \frac{6}{36} \). (b) The histogram is symmetric, peaking at 7, showing the most frequent sum.

Step by step solution

01

List Possible Outcomes

When rolling a pair of six-sided dice, each die has outcomes from 1 to 6. The sum of the spots showing on the dice, denoted by \( T \), ranges from 2 to 12. We'll list all combinations that lead to each possible value of \( T \).
02

Calculate Probability of Each Sum

There are 36 possible outcomes when rolling two dice (6 sides on the first die times 6 sides on the second die). For each sum \( T \), count how many combinations of die rolls result in that sum and divide by 36 to calculate the probability. For instance, \( T = 7 \) has 6 combinations: (1,6), (2,5), (3,4), (4,3), (5,2), and (6,1). Therefore, \( P(T=7) = \frac{6}{36} = \frac{1}{6} \). Repeat this for each possible \( T \).
03

Organize Probability Distribution

The probability distribution of \( T \) is given by listing each possible sum along with its probability: - \( T = 2 \rightarrow P(T = 2) = \frac{1}{36} \) - \( T = 3 \rightarrow P(T = 3) = \frac{2}{36} \) - \( T = 4 \rightarrow P(T = 4) = \frac{3}{36} \) - \( T = 5 \rightarrow P(T = 5) = \frac{4}{36} \) - \( T = 6 \rightarrow P(T = 6) = \frac{5}{36} \) - \( T = 7 \rightarrow P(T = 7) = \frac{6}{36} \) - \( T = 8 \rightarrow P(T = 8) = \frac{5}{36} \) - \( T = 9 \rightarrow P(T = 9) = \frac{4}{36} \) - \( T =10 \rightarrow P(T = 10) = \frac{3}{36} \) - \( T = 11 \rightarrow P(T = 11) = \frac{2}{36} \) - \( T = 12 \rightarrow P(T = 12) = \frac{1}{36} \).
04

Draw the Histogram

Create a histogram where each bar corresponds to a possible sum \( T \), from 2 to 12. The height of each bar represents the probability of that sum occurring. The highest bar should be at \( T = 7 \), descending symmetrically around it.
05

Describe the Histogram

The histogram is symmetric around \( T = 7 \), indicating that 7 is the most likely sum when rolling a pair of dice. The probabilities decrease as you move away from 7 towards the extremes, 2 and 12. This pattern reflects the number of ways each sum can be achieved with two dice.

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Key Concepts

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

Probability
Probability is a fundamental concept in statistics that measures the likelihood of an event happening. When rolling a pair of six-sided dice, each possible outcome of a sum has a specific probability associated with it. To determine the probability distribution of the sum of the spots, we first calculate the total number of possible outcomes. Given two dice, each can land on one of six faces, yielding a total of 36 combinations (6 sides on the first die times 6 sides on the second die).
For each possible sum (from 2 to 12), we count how many combinations result in that sum and then divide by 36. For example, the probability of rolling a sum of 7 is found by taking the 6 successful combinations (e.g., (1,6), (2,5), etc.) and dividing by 36, giving a probability of \( \frac{1}{6} \). This method applies to all possible sums.
Histogram
A histogram is a graphical representation used to organize a probability distribution. When you represent the probability distribution of the sum of dice using a histogram, each bar reflects the probability of a specific sum.
The x-axis of the histogram represents the sums (ranging from 2 to 12), while the y-axis shows the probability of each sum occurring. The height of each bar corresponds to the calculated probability. The histogram for the sum of dice rolls is symmetric and peaks at the value 7, which is the most probable outcome. It illustrates how sums less frequent than 7, such as 2 and 12, have lower bars, which means smaller probabilities.
  • Symmetric around 7
  • Descending towards the extremes 2 and 12
This symmetry highlights how rolling a 7 is more likely than rolling either a 2 or 12.
Combinatory Analysis
Combinatory analysis helps us understand how many different ways we can achieve a specific outcome when everything is considered. It's an essential technique when working with dice probabilities. By listing all possible dice combinations, we determine how often each sum appears. Each possible outcome (from 2 to 12) can be achieved by different pairings of dice rolls.
For example:
  • The sum of 2 is only possible with the combination (1,1), resulting in a probability of \( \frac{1}{36} \).
  • For a sum of 7, there are 6 combinations, like (1,6) and (3,4), offering a higher probability of \( \frac{1}{6} \).
The number of ways a sum can be achieved explains its probability. Combinatory analysis helps break down the problem and makes calculating these probabilities manageable.
Dice Statistics
Dice statistics involve studying the properties and outcomes of dice rolls. This includes understanding the sums that result from rolling two dice and the likelihood of these sums. Dice theory is a classical unit in probability, providing insights into likelihoods and distributions.
By analyzing sums of dice rolls, we learn:
  • The sum outcomes range from 2 to 12.
  • Sums near 7 appear more frequently due to more combinations achieving them.
  • Extremes, like 2 or 12, occur less frequently.
These insights reveal a crucial characteristic: certain sums are more likely than others. This pattern is significant, especially in games of chance or studies of randomness, as it helps us predict likely outcomes and their probabilities when rolling dice.

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