In a lottery where each ticket contains a unique combination of six numbers from 1 to 59, what is the probability of two people holding tickets with exactly one common number?

Instruction: Use combinatorics to calculate the overlap between two sets.

Context: The question assesses the candidate's understanding of combinatorial principles and set overlap in a practical context.

Official Answer

Certainly, that's an intriguing question! Let's dive into it with the perspective of a Data Scientist, as that aligns closely with the nature of the problem which involves probability and combinatorial analysis—a fundamental aspect of statistical theory, often encountered in data analysis and predictive modeling scenarios.

So, considering the scenario where we have a lottery with tickets containing a unique combination of six numbers from 1 to 59, we're looking to find the probability that two people have tickets with exactly one number in common. To tackle this, let's break down the problem into manageable parts and apply principles of combinatorics.

Firstly, it's important to recognize that the total number of ways to choose 6 numbers out of 59 is given by the combination formula C(n,r) = n! / [r!(n-r)!], where n is the total number of options (59 in this case), r is the number of selections (6 here), and ! denotes factorial, the product of all positive integers up to that number. Applying this, we find there are C(59,6) possible combinations for a lottery ticket.

Now, let's consider two people, A and B, each holding a ticket. For them to share exactly one number in common, let's fix one number that they both have. There are 59 options for this shared number. Once this number is fixed, person A's ticket must have 5 unique numbers not including the shared number, from the remaining 58 numbers. Therefore, there are C(58,5) ways to choose these numbers for person A.

For person B, to ensure exactly one number in common, we must exclude the 5 numbers that person A has (besides the shared number), leaving 53 numbers. Person B needs to choose all their remaining 5 numbers from these 53 (since choosing any of A's other numbers would increase the count of common numbers). Thus, there are C(53,5) ways for person B to choose their numbers under these conditions.

To find the probability, we divide the number of favorable outcomes by the total number of possible outcomes. The total number of ways two people can have tickets with exactly one number in common is 59 * C(58,5) * C(53,5). The total number of ways two people can have any ticket combination is C(59,6) * C(59,6) (since both are choosing independently from the full set). Thus, the probability is:

[ P = \frac{59 * C(58,5) * C(53,5)}{C(59,6) * C(59,6)} ]

In applying this formula, we're leveraging combinatorial logic to partition the problem into a structure that reflects the exact constraints (exactly one number in common), which is a technique often utilized in data science for hypothesis testing, data segmentation, and predictive analytics. It's a clear demonstration of how mathematical principles underpin the analysis of complex patterns and relationships within data.

By approaching the problem with this methodical breakdown, we not only arrive at the solution but also exemplify the analytical thinking and problem-solving skills that are critical in the field of data science. This approach allows us to dissect and understand the intricacies of the problem, paving the way for accurate, data-driven decision-making. It's a testament to the power of combining statistical knowledge with strategic thinking to tackle real-world challenges, a core competency in the realm of data science.

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