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Approximation of binomial to normal

The proportion of defective telephones manufactured on Mondays is 0.3. If a sample of 20 telephones is selected, what is the probability that 5 of the phones in the sample are defective? Use the normal distribution to approximate the binomial. Since this is a continuous distribution approximating a discrete distribution, use X values of 4.5 and 5.5. Show your work.
μ = np and σ = √ npq

Solution Preview

Using normal approximation we have

μ = np = 20*0.3 = 6

σ = √ npq ...