- #1

WendysRules

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## Homework Statement

In a manufacturing plant, a sample of a 100 items is taken from an assembly line. For each item in the sample, the probability of being defective is .06.

What is the probability that there are 3 or more defective units in the sample?

## Homework Equations

z = (x - mean)/standard deviation

mean = n*p

standard deviation = sqrt(n*p*(1-p)

## The Attempt at a Solution

Well, mean is just $$ 100*.06 = 6$$. The standard deviation is just $$ \sqrt{100*.06*.94} = 2.375 $$ so the Z = (3-6)/(2.375) = -3/2.375.

So, the prob(x>3) is just $$ 1- \frac{1}{\sqrt{2\pi}} \int^{-3/2.375}_{-\infty} e^{-.5x^2} dx = .8967 $$ Which isn't an answer choice I'm given. So, obviously, I did something wrong! Any help is appreciated.

Answer choices given: .7040, .8784, .9306, .8498, .8843.