Table of contents
- 1. Intro to Stats and Collecting Data55m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically1h 45m
- 4. Probability2h 16m
- 5. Binomial Distribution & Discrete Random Variables2h 33m
- 6. Normal Distribution and Continuous Random Variables1h 38m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
4. Probability
Counting
Problem 4.4.10
Textbook Question
Radio Station Call Letters Radio and Television station call letters must begin with either K (for stations west of the Mississippi River) or W (for stations east of the Mississippi River) and must include either two or three additional letters. How many different possibilities are there?

1
Step 1: Understand the structure of the call letters. Each call letter must begin with either 'K' or 'W', which gives us 2 choices for the first letter.
Step 2: Determine the number of additional letters. The problem states that there can be either 2 or 3 additional letters. Each additional letter can be any of the 26 letters in the English alphabet.
Step 3: Calculate the number of possibilities for 2 additional letters. For each of the 2 choices for the first letter ('K' or 'W'), there are 26 choices for the first additional letter and 26 choices for the second additional letter. The total number of possibilities for 2 additional letters is given by:
Step 4: Calculate the number of possibilities for 3 additional letters. Similarly, for each of the 2 choices for the first letter ('K' or 'W'), there are 26 choices for each of the 3 additional letters. The total number of possibilities for 3 additional letters is given by:
Step 5: Add the results from Step 3 and Step 4 to find the total number of possibilities. The total number of possibilities is:

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Combinatorics
Combinatorics is a branch of mathematics dealing with counting, arrangement, and combination of objects. In this context, it helps determine the number of possible combinations of letters that can form the call signs for radio stations. Understanding basic combinatorial principles, such as permutations and combinations, is essential for solving problems involving selection and arrangement.
Permutations and Combinations
Permutations refer to the different ways of arranging a set of items where the order matters, while combinations refer to the selection of items where the order does not matter. In the case of radio station call letters, we need to consider how many ways we can arrange the additional letters after the initial 'K' or 'W', which directly impacts the total number of unique call signs possible.
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Alphabetical Constraints
In this scenario, the call letters are constrained to the English alphabet, which consists of 26 letters. This limitation affects the total number of combinations possible for the additional letters in the call signs. Understanding how to apply these constraints is crucial for accurately calculating the total number of valid call letter combinations.
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