Question 478168
b. Estimate the probability P(at least 5) by using the normal distribution as an approximation to the binomial distribution with n= 15 and p = 0.4
Changing from binomial to normal approx: P(5<= x <=15) = P(4.5<= x <= 15.5)
u = np = 0.4*15 = 6 
sigma = sqrt(npq) = sqrt(0.4*15*0.6) = 1.9 when rounded to tenths
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z(4.5) = (4.5-6)/1.9 = -0.7895 
z(15.5) = (15.5-6)/1.9 = 5.0526
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P(x >= 5) is approximately P(-0.7895<= z <= 5.0526) = 0.7851
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c. Estimate the probability P(fewer than 7) by using the normal distribution as an approximation to the binomial distribution with n= 15 and p = 0.4
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Same procedure as above but find P(-0.5<= x <6.5)
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cheers,
Stan H.