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Grasshoppers are distributed at random in a large field according to a Poisson distribution with parameter \(\alpha=2\) per square yard. How large should the radius \(R\) of a circular sampling region be taken so that the probability of finding at least one in the region equals \(.99\) ?

Short Answer

Expert verified
The radius \(R\) should be approximately 1.384 yards.

Step by step solution

01

Understanding the Poisson Distribution

The number of grasshoppers (i.e., events) in a particular area follows a Poisson distribution with parameter \(\alpha = 2\). This means that the expected number of grasshoppers per square yard is \(2\).
02

Defining the Problem

We need a circular area where the probability of finding at least one grasshopper is \(0.99\). Let's find the radius \(R\) such that this condition holds true.
03

Finding the Required Probability Equation

The probability of finding at least one grasshopper in the circular region is dependent on the average number of grasshoppers expected in this area, given by \(A * \alpha\), where \(A\) is the area of the circle. The area \(A\) is \(\pi R^2\), thus the parameter becomes \(2\pi R^2\). The probability of finding no grasshopper is given by: \(P(X = 0) = e^{-2\pi R^2} = 1 - 0.99 = 0.01\)
04

Solving for Radius R

To solve for \(R\), calculate: \(e^{-2\pi R^2} = 0.01\). Taking the natural logarithm, we have: \(-2\pi R^2 = \ln(0.01)\). Simplify to find: \(R^2 = -\frac{\ln(0.01)}{2\pi}\). Then, solve for \(R\): \(R = \sqrt{-\frac{\ln(0.01)}{2\pi}} \approx 1.384\).

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Key Concepts

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

Probability
Probability is a measure of how likely an event is to occur. In the context of this problem, we're interested in understanding the likelihood that at least one grasshopper is found within a specific area. The probability here can be represented mathematically and calculated using a Poisson distribution. When we want the probability of finding at least one event (grasshopper) in a given area to be 0.99, we are essentially saying we want this event to happen almost certainly. This concept is essential in many real-world applications where decision-making under uncertainty is required. In this particular case, working with a Poisson distribution helps us express and solve the probability question quantitatively.
Circular Sampling Region
A circular sampling region is an area where measurements or observations are taken in a circular shape. This structure is common in various fields such as ecology, agriculture, or even quality control. In this problem involving grasshoppers, our circular region is defined by its radius, which we need to determine. Once we establish the radius, we can easily compute the area since the area of a circle is given by the formula \(A = \pi R^2\).In the context of this exercise, determining the correct sampling radius ensures that the probability of finding at least one grasshopper meets our desired threshold. Understanding regions like these can help efficiently allocate resources or plan further studies based on initial findings.
Expected Value
Expected value is a key concept in probability and statistics which indicates the average value one might anticipate from a random event following a specific probability distribution, in this case, the Poisson distribution. The expected value in a Poisson distribution with parameter \(\alpha\) gives the average number of events (grasshoppers) expected in a unit area, here specified as per square yard.For this problem, given that \(\alpha = 2\), the expected number of grasshoppers per square yard is 2. When the problem asks what circular region size gives a 99% chance of finding at least one grasshopper, it implies utilizing the concept of expected value to scale up the average occurrences to align with the desired probability. This calculation allows us to plan the sampling area optimally.
Natural Logarithm
Natural logarithms, denoted as \(\ln\), are logarithms to the base of the mathematical constant \(e\), where \(e\) approximates to 2.71828. In the context of solving probability problems like this one, we use natural logarithms to linearize exponential equations.In the original solution, we had the equation \(e^{-2\pi R^2} = 0.01\). To unravel the exponential nature, we took the natural logarithm on both sides, simplifying it to \(-2\pi R^2 = \ln(0.01)\). By transforming the equation this way, it becomes straightforward to solve for \(R\).Natural logarithms are a valuable tool in simplifying complex calculations and are widely used in various branches of science and engineering as well as finance and data analysis.

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