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Classify each random variable as either discrete or continuous. a. The number of boys in a randomly selected three-child family. b. The temperature of a cup of coffee served at a restaurant. c. The number of no-shows for every 100 reservations made with a commercial airline. d. The number of vehicles owned by a randomly selected household. e. The average amount spent on electricity each July by a randomly selected household in a certain state.

Short Answer

Expert verified
a: discrete, b: continuous, c: discrete, d: discrete, e: continuous.

Step by step solution

01

Identify the Nature of the Variable

A discrete random variable can take on a countable number of values, typically integers. A continuous variable can take on any value within a given range. We'll use this understanding to classify each variable.
02

Classify Variable a

The number of boys in a three-child family can only be 0, 1, 2, or 3, which are countable integers. Hence, this variable is discrete.
03

Classify Variable b

The temperature of coffee can vary continuously over a range and can take any value within that range. Therefore, it is a continuous variable.
04

Classify Variable c

The number of no-shows for reservations is a countable quantity (0, 1, 2,...). Therefore, it is a discrete variable.
05

Classify Variable d

The number of vehicles owned is countable and can be expressed in whole numbers, making it a discrete variable.
06

Classify Variable e

The average amount spent on electricity can take any value within a range, such as $25.50 or $100.75, therefore it is a continuous variable.

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Key Concepts

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

Discrete Random Variables
When you think about discrete random variables, visualize a series of distinct, separate values. These are values you can count, such as 1, 2, 3, and so on.
Discrete random variables don't have a middle ground between, say, 1 and 2. Examples from everyday life might include the number of eggs in a carton or the roll of a die.
To tie this to the exercise, consider the number of boys in a three-child family. The possibilities are 0, 1, 2, or 3. Since these outcomes are limited and countable, it is a discrete random variable.
  • Another instance is the number of no-shows for reservations. Countable events like this (e.g., 0, 1, 2,...) also qualify as discrete variables.
  • The number of vehicles a family owns is finite and countable, making it another good example of a discrete random variable.
In each scenario, what you count is a complete, whole number. Discrete random variables are often easy to understand as they align with our natural counting process.
Continuous Random Variables
Continuous random variables, on the other hand, can take any value within a certain range.
Imagine something that can be finely divided, such as measuring the exact temperature of a cup of coffee or the precise amount of rain falling in an hour. These values are not just whole numbers.
They could be 21.3, 21.4, or even 21.35. This makes continuous variables particularly useful in real-world measurements.
  • The temperature of coffee is a great example, as it varies from one moment to the next, with potentially infinite precision between degrees.
  • Similarly, the average amount spent on electricity can be any figure within a range. It doesn't restrict itself to whole numbers because costs fluctuate with high precision.
The key feature of continuous variables is that there isn't a smallest possible unit of measurement they rely on. Instead, they offer a seamless range of potential outcomes.
Statistical Classification
Statistical classification is a process used to organize data based on shared attributes. In the context of random variables, it helps us distinguish between different types of statistical data like discrete and continuous.
The classification process involves identifying whether the data you're working with is a countable series of whole numbers, or if it involves a continuum of values.
  • Classifying data correctly is essential as it informs which statistical methods to apply.
  • Discrete data might be best analyzed using frequency counts or probability distributions specific to finite sets.
  • Continuous data, however, might require techniques like calculus-based probability density functions or statistical modeling involving continuous distributions.
When approached with a clear understanding, statistical classification sets the foundation for precise and appropriate analysis, allowing for accurate interpretation of real-world phenomena.

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Most popular questions from this chapter

Identify the set of possible values for each random variable. (Make a reasonable estimate based on experience, where necessary.) a. The number of hearts in a five-card hand drawn from a deck of 52 cards that contains 13 hearts in all. b. The number of pitches made by a starting pitcher in a major league baseball game. c. The number of breakdowns of city buses in a large city in one week. d. The distance a rental car rented on a daily rate is driven each day. e. The amount of rainfall at an airport next month.

A coin is bent so that the probability that it lands heads up is \(2 / 3\). The coin is tossed ten times. a. Find the probability that it lands heads up at most five times. b. Find the probability that it lands heads up more times than it lands tails up.

Seven thousand lottery tickets are sold for \(\$ 5\) each. One ticket will win \(\$ 2,000,\) two tickets will win \(\$ 750\) each, and five tickets will win \(\$ 100\) each. Let \(X\) denote the net gain from the purchase of a randomly selected ticket. a. Construct the probability distribution of \(X\). b. Compute the expected value \(E(X)\) of \(X .\) Interpret its meaning. c. Compute the standard deviation \(\sigma\) of \(X\).

An insurance company will sell a \(\$ 90,000\) one-year term life insurance policy to an individual in a particular risk group for a premium of \(\$ 478\). Find the expected value to the company of a single policy if a person in this risk group has a \(99.62 \%\) chance of surviving one year.

Two fair dice are rolled at once. Let \(X\) denote the difference in the number of dots that appear on the top faces of the two dice. Thus for example if a one and a five are rolled, \(x=4,\) and if two sixes are rolled, \(X=0\). a. Construct the probability distribution for \(X\). b. Compute the mean \(\mu\) of \(X\). c. Compute the standard deviation \(\sigma\) of \(X\).

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