# 3.6 Geometric Probability using the Excel Sheet provided

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Suppose the probability that a red car enters an intersection is 0.24.  What is the probability 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

To find the probability P(X = 5) follow the steps below.

• Step 1: Enter 0.24 in cell B1 and hit the Enter key.
• Step 2: Find 5 in column A at cell A9.
• Step 3: Move to column B, cell B9.  The answer is 0.0801

To find the probability P(X < 8), follow the steps below.

• Step 1: Find 8 in column A at cell A12.
• Step 2: Move to column B, cell B12.  The answer is 0.8887.

To find the probability P(X > 10), follow the steps below.

• Step 1: Find 9 in column A at cell A13.
• Step 2: Move to column C, cell C13.  The answer is 0.9154.
• Step 3: Subtract 0.9154 from 1, (1 - 0.9154 = 0.0846).

To find the probability P(X < 7) = P(X < 6), follow the steps below.

• Step 1: Find 6 in column A at cell A10.
• Step 2: Move to column C, cell C10.  The answer is 0.9357.

To find the probability P(X > 4) = P(X > 5), follow the steps below.

• Step 1: P(X > 5) = 1 - P(X < 4).
• Step 2: Find 4 in column A at cell A8.
• Step 3: Move over to cell C8, 0.6664.
• Step 4: Subtract 0.6664 from 1, 1 - 0.6664 = 0.3336.

The Mean is in cell F1, 4.16667.

The Variance is in cell F2, 13.1944.

The Standard Deviation is in cell F3, 3.63.

##### Interactive Element

3.6 Geometric Probability using the Excel Sheet provided is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.