The POISSON.DIST function in Google Sheets is a powerful statistical tool that enables users to compute the Poisson distribution. This distribution is useful for modeling the number of events that occur within a fixed interval of time or space, particularly when these events happen with a known constant mean rate and independently of the time since the last event. Understanding how to use this function can significantly enhance data analysis and statistical reporting.

Syntax

POISSON.DIST(x, mean, cumulative)

• x: The actual number of successful events (e.g., occurrences) that you are evaluating.
• mean: The expected mean number of occurrences over the interval.
• cumulative: A logical value that determines the form of the function. If TRUE, it returns the cumulative distribution function; if FALSE, it returns the probability mass function.

Example #1

POISSON.DIST(3, 2, FALSE)

This function calculates the probability of observing exactly 3 events, given an average of 2 events. The result is approximately 0.180.

Example #2

POISSON.DIST(5, 3, TRUE)

This function calculates the cumulative probability of observing up to 5 events when the average number of events is 3. The result is around 0.857.

Example #3

POISSON.DIST(7, 5, FALSE)

This evaluates the probability of observing exactly 7 events with an average of 5. The result is about 0.104.

Error handling

• NUM!: This error occurs if the values for x or mean are less than zero, as they must be non-negative numbers.
• VALUE!: This error appears when the cumulative parameter is not a logical value (i.e., TRUE or FALSE).

Conclusion

The POISSON.DIST function in Google Sheets is an invaluable resource for statistical analysis, particularly in scenarios involving counting occurrences in fixed contexts. By understanding its parameters and utilizing the examples provided, users can effectively leverage this function to gain insights from their data and improve decision-making processes.