The POISSON function in Google Sheets is a powerful statistical tool used to compute the probability of a given number of events occurring within a specified interval. It leverages the Poisson distribution, which is ideal for modeling the frequency of events in a fixed period of time or space, particularly when these events are independent. This function is widely used in various fields such as finance, insurance, and research, allowing users to analyze probabilities effectively.

Syntax

=POISSON(x, mean, cumulative)

• x: The actual number of events that occur.
• mean: The expected number of events (average) in the specified interval.
• cumulative: A boolean value that determines the form of the function. If TRUE, it returns the cumulative probability; if FALSE, it returns the probability mass function.

Example #1

=POISSON(3, 2, FALSE)

In this example, the function calculates the probability of exactly 3 events occurring when the average is 2. The result would be approximately 0.180.

Example #2

=POISSON(5, 3, TRUE)

Here, it computes the cumulative probability of 5 or fewer events occurring when the mean is 3. The resulting value would be around 0.857.

Example #3

=POISSON(2, 4, FALSE)

This function evaluates the probability of exactly 2 events occurring when the average is 4. The result would be close to 0.195.

Error handling

• VALUE!: This error occurs if the input for x or mean is non-numeric or if cumulative isn’t TRUE or FALSE.
• NUM!: This error indicates that x is a negative number, which is invalid for this function.

Conclusion

In summary, the POISSON function is essential for analyzing the probability of events over fixed intervals. By understanding its syntax and potential error messages, users can effectively apply this function to various real-world scenarios, enhancing their data analysis capabilities within Google Sheets.