In Google Sheets, the LOGNORMDIST function calculates the cumulative distribution function (CDF) of the log-normal distribution.

It returns the probability that a random variable from a log-normal distribution is less than or equal to a specified value.

The function takes three arguments:

x: This is the value for which you want to calculate the CDF.

mean: This is the mean of the log-normal distribution.

standard_deviation: This is the standard deviation of the log-normal distribution.

The formula for the log-normal distribution is:

LOGNORMDIST(x, mean, standarddeviation) = Φ((ln(x) - mean) / standarddeviation)

Where Φ is the cumulative standard normal distribution function.

It's important to note that the x value must be positive. If x is zero or negative, the LOGNORMDIST function will return the #NUM! error.

Here's an example of how to use the LOGNORMDIST function in Google Sheets:

=LOGNORMDIST(10, 2, 1.5)

This formula calculates the probability that a random variable from a log-normal distribution with a mean of 2 and a standard deviation of 1.5 is less than or equal to 10.

Remember to replace the arguments mean and standard_deviation with the appropriate values for your specific use case.