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Use the following information to answer the next four exercises: Ellen has music practice three days a week. She practices for all of the three days 85% of the time, two days 8% of the time, one day 4% of the time, and no days 3% of the time. One week is selected at random. We know that for a probability distribution function to be discrete, it must have two characteristics. One is that the sum of the probabilities is one. What is the other characteristic?

Short Answer

Expert verified
The second characteristic is that each probability must be between 0 and 1, inclusive.

Step by step solution

01

Understanding a Discrete Probability Distribution

A discrete probability distribution consists of a list of possible outcomes along with the probability for each outcome. Each outcome is associated with a distinct probability.
02

Review of Characteristics of a Discrete Distribution

The first important characteristic of a discrete probability distribution is that the sum of all probabilities must equal one. This indicates that the distribution accounts for all possible outcomes.
03

Identifying the Second Characteristic

The second characteristic of a discrete probability distribution is that the probability of each event must be between 0 and 1, inclusive. This means no outcome can have a probability less than 0 or greater than 1.

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Key Concepts

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

Probability Distribution Functions
Probability distribution functions are essential in understanding how probabilities are assigned to discrete events. These functions provide a complete overview of possible outcomes and their respective probabilities in a discrete setting. In Ellen's music practice example, we have various outcomes鈥攑racticing all three days, two days, one day, or not at all. Each of these outcomes has a specific probability linked to them. A probability distribution function is discrete if it represents events that can be counted individually, like the days Ellen practices music. For Ellen, the probabilities are presented as:
  • Practicing three days: 85%
  • Practicing two days: 8%
  • Practicing one day: 4%
  • Not practicing at all: 3%
These outcomes must add up to 100% or 1 in probability terms, confirming they account for all possibilities during the week.
Probability Characteristics
There are specific characteristics that a discrete probability distribution must have to be valid. The first key characteristic is that the sum of all probabilities in the distribution must equal one. This means that when you add the probabilities of all possible outcomes, they should total 100%. If the sum is anything other than one, the distribution cannot be considered complete or accurate. The second crucial characteristic requires each individual outcome's probability to be between 0 and 1, inclusive. This implies that no probability can be negative or greater than 100%. For example, if Ellen had a 105% chance of practicing three days, this would not be possible because probabilities cannot exceed 100%.
Discrete Probability Concepts
Understanding discrete probability concepts is vital for analyzing situations like Ellen's music practice. Discrete probability deals with outcomes that are distinct and countable, such as the number of days Ellen practices during the week. Unlike continuous probability, which deals with probabilities across a continuum, discrete probability handles scenarios where outcomes fall into distinct sets or groups. When you consider the discrete nature of these probabilities, it helps to simplify and clarify the options at hand. Using Ellen's practice schedule as an example, you can clearly see each event's probability and how it contributes to the overall distribution. For students, grasping these discrete concepts can enhance their understanding of probability problems, making it easier to break down and analyze any similar situations they might encounter in their studies.

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