Formulas and Functions

Chapter 10 Statistical Functions 283
 probability-values: The collection containing the probability values. probability-
values is a collection containing number values. The sum of the probabilities must
add up to 1. Any string values are ignored.
 lower: The lower limit or bound. lower is a number value.
 upper: An optional upper limit or bound. upper is a number value and must be
greater than or equal to lower.
Usage Notes
The PROB function sums the probabilities associated with all values in the collection Â
greater than or equal to the specied lower limit value and less than or equal to the
specied upper limit value. If upper is omitted, PROB returns the probability of the
single number equal to the specied lower limit.
The two arrays must be of the same size. If text is contained in an array, it will be Â
ignored.
Examples
Assume you are thinking of a number from 1 to 10 to have someone guess. Most people would say
the probability that you would be thinking of a particular number is 0.1 (10%), as listed in column
C, since there are ten possible choices. However, studies have shown that people do not choose
numbers randomly.
Assume that a study has shown that people like you are more likely to select certain numbers than
others. These revised probabilities are in column E.
=PROB(A1:A10, C1:C10, 4, 6) returns 0.30, the probability that the value is 4, 5, or 6, assuming choices
are completely random.
=PROB(A1:A10, E1:E10, 7) returns 0.28, the probability that the value is 4, 5, or 6, based on the research
that numbers are not chosen randomly.
=PROB(A1:A10, E1:E10, 4, 6) returns 0.20, the probability that the value is 7, based on the research that
numbers are not chosen randomly.
=PROB(A1:A10, C1:C10, 6, 10) returns 0.50, the probability that the value is greater than 5 (6 to 10),
assuming choices are completely random.