A clothing manufacturer estimates from past quality control inspections that 4.8% of sweatshirts produced are irregular. If an inspector randomly selects 650 sweatshirts, estimate the probability that at least 30 are irregular.
np = 350x0.10 = 35
n(1-p) =350 x 0.90 = =315
np>=5, n(1-p) >=5
Therefore, the approximation is resonably close to a normal distribution because
np <= 5 and n(1-p) >=5
Now I can calculate the standard deviation
mean = np =35
sd= sqr(npq) =5.61
How do I calculate the probability?
"In mathematics, you don't understand things. You just get used to them." -- Johann von Neumann