Question

A manufacturer of computer disks has a historical defective rate of .001. what is the probability that in a batch oof 1000 disks, 2 would be defective?

Answer 1

p(2 defective) = 1000C2*(.001²)*(.999⁹⁹⁸)

.. ≈ 499,500*10⁻⁶*0.368432

.. ≈ 0.18403

About 18.4%.

Answer 2

p(2 defective) = 1000C2*(.001²)*(.999⁹⁹⁸)
.. ≈ 499,500*10⁻⁶*0.368432
.. ≈ 0.18403

About 18.4%.