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Let \(x\) be a Poisson random variable. Using the Poisson probabilities table, write the probability distribution of \(x\) for each of the following. Find the mean, variance, and standard deviation for each of these probability distributions. Draw a graph for each of these probability distributions. a. \(\lambda=.6\) b. \(\lambda=1.8\)

Short Answer

Expert verified
For \( \lambda=0.6 \), the mean, variance and standard deviation are 0.6, 0.6 and \( \sqrt{0.6} \) respectively. For \( \lambda=1.8 \), these values are 1.8, 1.8 and \( \sqrt{1.8} \) respectively. The graphs would be a better visualization for the distribution in both cases.

Step by step solution

01

Finding the Probability, Mean, Variance and Standard Deviation for \( \lambda=0.6 \)

1. For a Poisson distribution, the formula for probability is \( P(x; \lambda) = e^{-\lambda} \lambda^x / x! \), where 'x' is the actual number of successes that result from the experiment, and 'e' is approximately equal to 2.71828. \n For \( \lambda=0.6 \), substitute in the formula to get the respective probabilities. 2. The mean and variance of a Poisson distributed random variable are both equal to \( \lambda \). So, the mean and variance for this distribution is \( \lambda=0.6 \). 3. The standard deviation is the square root of \( \lambda \), so standard deviation = \( \sqrt{0.6} \). 4. Use these probabilities to plot a graph.
02

Finding the Probability, Mean, Variance and Standard Deviation for \( \lambda=1.8 \)

1. Use the Poisson formula for probability distribution for each possible value of \( x \) with \( \lambda=1.8 \). 2. As with the previous distribution, the mean and variance are equal to \( \lambda \), so they are both 1.8.3. The standard deviation is the square root of \( \lambda \), so standard deviation = \( \sqrt{1.8} \).4. Plot the graph using the calculated probabilities.
03

Drawing the Graphs for Both Cases

Draw the graphs for both situations, with 'x' on the x-axis representing the number of occurrences and the 'Probability' on the y-axis. Each point on the graph shows the probability of 'x' number of occurrences. You could use bars to represent these probabilities and have two different sets of bars for both situations.

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Key Concepts

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

Probability Distribution
In statistics, a probability distribution is an essential concept that helps in understanding how probabilities are allocated over possible outcomes. When dealing with a Poisson distribution, the probability of a given number of events occurring in a fixed interval is defined by the formula:\[ P(x; \lambda) = \frac{e^{-\lambda} \lambda^x}{x!} \]where:- \( x \) is the number of events,- \( \lambda \) (lambda) is the average number of events within the interval,- \( e \) is the base of the natural logarithm, approximately 2.71828.For each specific outcome \( x \), this formula provides the probability of \( x \) events happening. Hence, when \( \lambda = 0.6 \) or \( \lambda = 1.8 \), calculating this for various values of \( x \) will result in the probability distribution of these events over time. This forms a crucial part of understanding how likely different scenarios are, based on past occurrences.
Mean and Variance
The mean and variance are foundational concepts in statistics, giving insights into the behavior of probability distributions. For a Poisson distribution, these two measures are uniquely straightforward:- The mean (\( \mu \)) is simply equal to \( \lambda \).- Similarly, the variance (\( \sigma^2 \)) also equals \( \lambda \).Therefore, when \( \lambda \) is 0.6 and 1.8 respectively, both the mean and variance are equal to these values. What this implies is that, for a Poisson distribution, the average rate of occurrence comprises both its expected value and the spread around that mean. Having both mean and variance as \( \lambda \) simplifies calculations and provides a direct insight into how data points are distributed around the center. Understanding these attributes is vital in predicting the likelihood and dispersion of random events in the given interval.
Standard Deviation
Standard deviation is a measure that quantifies the amount of variation or dispersion in a set of data values. It is particularly useful in understanding the spread of a probability distribution. For a Poisson distribution, the standard deviation is the square root of \( \lambda \):\[ \sigma = \sqrt{\lambda} \]So, for \( \lambda = 0.6 \), the standard deviation is \( \sqrt{0.6} \), and for \( \lambda = 1.8 \), it's \( \sqrt{1.8} \). Standard deviation informs us about how much the outcomes deviate from the average or mean value. It is important because it provides a sense of the typical distance of data points from the mean, aiding in the understanding of variability within the distribution of events. The lower the standard deviation, the closer data points tend to be to the mean, while a higher standard deviation indicates a wider spread of outcomes.
Graphing Probability Distributions
Visualizing probability distributions can greatly enhance understanding, making complex concepts more tangible. For a Poisson distribution, graphs typically involve plotting \( x \) (the number of events) on the x-axis against their probabilities on the y-axis. This forms a bar graph showing the likelihood of different outcomes. Each bar height represents the probability of that outcome.For instance, when plotting with \( \lambda = 0.6 \) and \( \lambda = 1.8 \), we draw separate graphs to depict each scenario. Every graph provides a visual representation of how probabilities are distributed. It shows which events are most likely and which are less probable. Using graphs, it becomes clearer how different values of \( \lambda \) alter the shape and spread of the distribution, assisting in a more intuitive comprehension of the data's behavior over time.These visual aids are instrumental in identifying patterns and better predicting potential outcomes in probabilistic scenarios.

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