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# A to Z of Excel Functions: The PROB Function

5 February 2024

Welcome back to our regular A to Z of Excel Functions blog.  Today we look at the PROB function.

The PROB function

I have no PROB with this function.  It returns the probability that values in a range (to be specified) are between two limits.  If the upper limit is not specified, PROB returns the probability that the value in the x_range is equal to the lower limit.

The PROB function uses the following syntax to operate:

PROB(x_range, probability_range, lower_limit, [upper_limit])

The PROB function has the following arguments:

• x_range: this is required and represents the range of numerical values of x with which there are associated probabilities
• probability_range: this is also required, and denotes a set of probabilities associated with the values in the x_range
• lower_limit:this is required and cites the lower bound on the value for which you want a probability
• upper_limit: this argument is optional and represents the upper bound on the value for which you require a probability.

It should be further noted that:

• if any value in probability_range ≤ 0 or if any value in probability_range > 1, PROB returns the #NUM! error value
• if the sum of the values in probability_range is not equal to 1, PROB returns the #NUM! error value
• if upper_limit is omitted, PROB returns the probability of being equal to the lower_limit
• if x_range and probability_range contain a different number of data points, PROB returns the #N/A error value.