How to use Excel function for Geometric
Suppose the probability that a red car enters an intersection is 0.24. What is the likelihood that the first red car enters the intersection after four non-red vehicles pass through the intersection? The discrete probability distribution is Geometric.
P(Red Car) = .24
P(Not Red Car) = 1-.24 = .76
P( X = 5) = (.76)4(.24) = 0.0801 Rounded to 4 decimal places
To compute the probability in an Excel spreadsheet, enter the formula below.
=NEGBINOM.DIST(4, 1, 0.24, FALSE)
- 4 represents the four non-red cars that have entered the intersection before the red car.
- 1 represents the first red car that enters the intersection.
- 0.24 is the probability of a red car entering the intersection.
- False means you want to compute a probability for one value, P(X = 5).
- True means you want to compute the P(X < 5).
The answer you should see is 0.080069. Rounded to four decimal
You can also enter the following formula for one probability
To make sure the formula is calculated, hit the Enter key after entering the formula.
Interactive Element: Live Excel Spreadsheet
Next, find the probability that at most 4 white cars pass through the intersection during one hour.
The probability statement is P(X < 4). The Excel function is =NEGBINOM.DIST(3, 1, 0.24, True) . The answer is 0.6664 rounded to 4 decimal places.