The Poisson Distribution Calculator will construct a complete poisson distribution, and identify the mean and standard deviation.  A poisson probability is the chance of an event occurring in a given time interval.  Enter $\lambda$ and the maximum occurrences, then the calculator will find all the poisson probabilities from 0 to max.  If you want to find the poisson probability for a specific occurrence only, then have a look at the Poisson Probability Calculator.

The Poisson Distribution Calculator will construct a complete poisson distribution, and identify the mean and standard deviation.

Enter a value for $\lambda$ and x.  Lambda, $\lambda$, is the average number of occurrences for a given time interval.  x is the maximum number of occurrences.  The calculator will display the poisson distribution, the mean, and the standard deviation.  Then, it will also give you a step by step solution for how to find poisson probabilities.

Poisson Distribution Calculator

Answer:

Mean of the Poisson Distribution, $\mu$: 6.9
Standard Deviation of the Poisson Distribution, $\sigma$: 2.6267851073127

P(0) = 0.0010077854290485
P(1) = 0.0069537194604347
P(2) = 0.0239903321385
P(3) = 0.05517776391855
P(4) = 0.095181642759498
P(5) = 0.13135066700811
P(6) = 0.15105326705932
P(7) = 0.14889536324419
P(8) = 0.12842225079811


Solution:

The mean of the poisson distribution is interpreted as the mean number of occurrences for the distribution. By definition, $\lambda$ is the mean number of successes for a poisson distribution. For this distribution, the mean is $$ \mu = \lambda = 6.9 $$

The standard deviation of the poisson distribution is interpreted as the standard deviation of the number of occurences for the distribution. To find the standard deviation, use the formula $$ \sigma = \sqrt{\lambda} $$ Substituting in the value of $\lambda$ for this problem, we have $$ \sigma = \sqrt{6.9} $$ Evaluating the expression on the right, we have $$ \sigma = 2.6267851073127 $$

To complete a poisson distribution table, first identify all of the possible values of X. Since the maximum number of occurences is 8, the values of X range from X = 0 to X = 8.

Next, find each individual poisson probability for each value of X. In this problem, we will be finding 9 probabilities. The sum of all these probabilities will be 1.


$P(0)$ Probability of exactly 0 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 0 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 0 $ and $ \lambda = 6.9 $, we have $$ P(0) = \frac{{e^{-6.9}} \cdot {6.9^0}}{0!} $$ Remember, 0! is 1. Evaluating the expression, we have $$ P(0) = 0.0010077854290485 $$


$P(1)$ Probability of exactly 1 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 1 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 1 $ and $ \lambda = 6.9 $, we have $$ P(1) = \frac{{e^{-6.9}} \cdot {6.9^1}}{1!} $$ Evaluating the expression, we have $$ P(1) = 0.0069537194604347 $$


$P(2)$ Probability of exactly 2 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 2 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 2 $ and $ \lambda = 6.9 $, we have $$ P(2) = \frac{{e^{-6.9}} \cdot {6.9^2}}{2!} $$ Evaluating the expression, we have $$ P(2) = 0.0239903321385 $$


$P(3)$ Probability of exactly 3 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 3 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 3 $ and $ \lambda = 6.9 $, we have $$ P(3) = \frac{{e^{-6.9}} \cdot {6.9^3}}{3!} $$ Evaluating the expression, we have $$ P(3) = 0.05517776391855 $$


$P(4)$ Probability of exactly 4 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 4 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 4 $ and $ \lambda = 6.9 $, we have $$ P(4) = \frac{{e^{-6.9}} \cdot {6.9^4}}{4!} $$ Evaluating the expression, we have $$ P(4) = 0.095181642759498 $$


$P(5)$ Probability of exactly 5 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 5 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 5 $ and $ \lambda = 6.9 $, we have $$ P(5) = \frac{{e^{-6.9}} \cdot {6.9^5}}{5!} $$ Evaluating the expression, we have $$ P(5) = 0.13135066700811 $$


$P(6)$ Probability of exactly 6 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 6 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 6 $ and $ \lambda = 6.9 $, we have $$ P(6) = \frac{{e^{-6.9}} \cdot {6.9^6}}{6!} $$ Evaluating the expression, we have $$ P(6) = 0.15105326705932 $$


$P(7)$ Probability of exactly 7 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 7 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 7 $ and $ \lambda = 6.9 $, we have $$ P(7) = \frac{{e^{-6.9}} \cdot {6.9^7}}{7!} $$ Evaluating the expression, we have $$ P(7) = 0.14889536324419 $$


$P(8)$ Probability of exactly 8 occurrences

If using a calculator, you can enter $ \lambda = 6.9 $ and $ x = 8 $ into a poisson probability distribution function (poissonPDF). If doing this by hand, apply the poisson probability formula: $$ P(x) = \frac{{e^{-\lambda}} \cdot {\lambda^x}}{x!} $$ where $x$ is the number of occurrences, $\lambda$ is the mean number of occurrences, and $e$ is the constant 2.718. Substituting in values for this problem, $ x = 8 $ and $ \lambda = 6.9 $, we have $$ P(8) = \frac{{e^{-6.9}} \cdot {6.9^8}}{8!} $$ Evaluating the expression, we have $$ P(8) = 0.12842225079811 $$

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