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A Taste Test. A tea-drinking Canadian friend of yours claims to have a very refined palate. She tells you that she can tell if, in preparing a cup of tea, milk is first added to the cup and then hot tea poured into the cup or the hot tea is first poured into the cup and then the milk is added. \(1 .\) To test her claims, you prepare six cups of tea. Three have the milk added first and the other three the tea first. In a blind taste test, your friend tastes all six cups and is asked to identify the three that had the milk added first. a. How many different ways are there to select three of the six cups? (Hint: See Example 12.8, page 281.) b. If your friend is just guessing, what is the probability that she correctly identifies the three cups with the milk added first?

Short Answer

Expert verified
a. 20 ways; b. Probability is \( \frac{1}{20} \).

Step by step solution

01

Understand the Combination Problem

The problem involves choosing 3 cups out of 6, where the combination formula is used because the order of selection does not matter.
02

Calculate Total Combinations

We use the combination formula \( C(n, r) = \frac{n!}{r! \times (n-r)!} \) to find the number of ways to choose 3 cups out of 6. Here, \( n = 6 \) and \( r = 3 \).
03

Plug Values into Combination Formula

Substitute into the formula: \( C(6, 3) = \frac{6!}{3! \times (6-3)!} = \frac{6 \times 5 \times 4}{3 \times 2 \times 1} = 20 \). Therefore, there are 20 different ways to select 3 cups out of 6.
04

Calculate Probability of Correct Guessing

The probability of your friend guessing the three cups correctly is the number of successful outcomes (one set of 3 cups) divided by the total number of possible combinations (20).
05

Find the Probability Value

The probability is \( \frac{1}{20} \) because there is only 1 correct set of 3 cups with milk added first, from 20 possible sets.

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Key Concepts

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

Combination Formula
The concept of the combination formula is pretty straightforward and is crucial in many probability and statistics problems. It is used to determine how many ways you can choose a subset of items from a larger set, without caring about the order. This is extremely helpful in situations like our taste test problem, where the order doesn't matter.

The combination formula is denoted as \( C(n, r) \), which you might see as \( \binom{n}{r} \). It calculates the number of ways to choose \( r \) items from a set of \( n \) items. The formula is:
  • \( C(n, r) = \frac{n!}{r! \times (n-r)!} \)
In this context, \( n! \) (n factorial) means multiplying all whole numbers from \( n \) down to 1.
  • For instance, \( 5! = 5 \times 4 \times 3 \times 2 \times 1 = 120 \).
So, in the setup of choosing 3 cups out of 6, you've set \( n = 6 \) and \( r = 3 \). With the combination formula, you find 20 different ways this selection can be made.
Blind Taste Test
Blind taste tests are not only fun but also a valuable method in experiments to test the reliability of taste perceptions. The idea is to mask information that could influence the test outcome, such as knowing the order or preparation of food and drinks.

In a blind taste test, the participant does not know which item they're tasting, allowing them to rely solely on their senses rather than preconceived notions or biases. This method ensures that the test focuses entirely on taste detection rather than memory.
  • For our tea test, this means that your tea-loving friend isn't told which cups have the milk added first, avoiding any bias.
  • This setup is common in product testing to evaluate if people can really tell differences between products or if their perceptions are influenced by branding, marketing, or other factors.
Thus, we can objectively gauge if distinctions can be made based on her true taste ability, independently confirming or debunking her claims.
Combinatorics
Combinatorics is a fascinating area of mathematics focusing on counting, arrangement, and combination of elements within sets. It is like putting together the building blocks of all the ways to order or pick from a given set.

At the heart of combinatorics are combination and permutation calculations. The combination formula, as explained, selects subsets without considering order, whereas permutations do care about the order of arrangement. However, in our specific tea test case, we focus on combinations because order doesn't matter.
  • Combinatorial problems often deal with questions like, "How many different groups can you form?" or "In how many ways can a task be done?"
In scenarios like our blind taste test, combinatorics helps determine the probability of various outcomes, such as correctly identifying which cups had milk added first purely by chance. Here, the exercise of choosing 3 cups from 6 shows how combinatorics offers answers through calculated combinations and provides the groundwork to understand probability in real-world setups.

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