How do you calculate POS?

• A. POS = POD / POC
• B. POS = POC x POD
• C. POS = POC + POD
• D. POS = POD - POC

Answer: (B)

The calculation hinges on combining two probabilities that must both occur. If POC is the chance of passing the first stage and POD is the chance of passing the second stage, and these events are independent, the overall chance of success through both stages is the product: POS = POC × POD. This follows the rule for independent events: the probability of both happening is the product of their probabilities.

For example, if POC is 0.8 and POD is 0.9, then POS is 0.72. Multiplying them correctly captures the likelihood of a successful outcome requiring both steps to occur. Using addition or subtraction would misrepresent the joint probability, and division wouldn’t reflect the need for both conditions to be satisfied. If the events aren’t independent, a more complex treatment would be needed, but with independence, multiplication is the right approach.