Question 252592
probability of exactly 0 defective products in a batch is equal to .96^20 = .442002434


probability of exactly 1 defective product in a batch is equal to 20 * .04*.96^19 = .368335362


the probability that at least 2 will be defective is 1 minus the probability of (exactly 0 defective and exactly 1 defective).  


This equals 1 - (.442002434 + .368335362) = .189662205.


If I did this correctly, the probability that at least 2 will be defective in a batch is 18.96%.