A batch of one hundred bulbs is inspected by testing four randomly chosen bulbs. The batch is rejected if even one of the bulbs is defective. A batch typically has five defective bulbs. The probability that the current batch is accepted is

0.8145
0.8155
0.8150
0.8160

Correct answer: 0.8145

Solution

The batch is accepted only if all 4 tested bulbs are non-defective. Since there are 95 good bulbs out of 100, the probability is \(\frac{\binom{95}{4}}{\binom{100}{4}}\). This evaluates to approximately 0.8145.

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