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
5. Binomial Distribution & Discrete Random Variables
Discrete Random Variables
Problem 4.3.6
Textbook Question
In Exercises 5–8, find the indicated probability using the Poisson distribution.
P(3) when μ = 6

1
Understand the Poisson distribution formula: P(x; μ) = (e^(-μ) * μ^x) / x!, where x is the number of occurrences, μ is the mean number of occurrences, and e is the base of the natural logarithm (approximately 2.718).
Identify the given values in the problem: x = 3 (the number of occurrences) and μ = 6 (the mean number of occurrences).
Substitute the given values into the formula: P(3; 6) = (e^(-6) * 6^3) / 3!.
Simplify the numerator: Calculate e^(-6), then multiply it by 6^3 (6 raised to the power of 3).
Simplify the denominator: Calculate 3! (3 factorial, which is 3 * 2 * 1), and then divide the numerator by this value to find the probability.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Poisson Distribution
The Poisson distribution is a probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time or space, given that these events occur with a known constant mean rate and independently of the time since the last event. It is particularly useful for modeling rare events.
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Parameter (μ)
In the context of the Poisson distribution, the parameter μ (mu) represents the average number of events in the specified interval. It is a crucial component for calculating probabilities, as it defines the shape and scale of the distribution. For example, if μ = 6, it indicates that, on average, 6 events are expected to occur.
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Probability Mass Function (PMF)
The Probability Mass Function (PMF) of a discrete random variable gives the probability that the variable is equal to a specific value. For the Poisson distribution, the PMF is calculated using the formula P(X = k) = (e^(-μ) * μ^k) / k!, where k is the number of events, e is Euler's number, and k! is the factorial of k. This formula allows us to find the probability of observing exactly k events.
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