An average light bulb manufactured by the Acme Corporation lasts 300 days with a

Question

An average light bulb manufactured by the Acme Corporation lasts 300 days with a standard deviation of 50 days. Assuming that bulb life is normally distributed:
1. What is the probability that an Acme light bulb will last more than 300 days?
2. What is the probability that an Acme light bulb will last less than 300 days?
3. What is the probability that an Acme light bulb will last exactly 300 days?
4. In order to obtain a scientific survey with 95 % confidence level of public opining on something without making more than 3% error in either direction, how much percentage of all American adults should we ask?

Explanation / Answer

Given X~Normal(mean=300, s=50) 1. What is the probability that an Acme light bulb will last more than 300 days? P(X>300) = P((X-mean)/s > (300-300)/50) =P(Z>0) =0.5 (check standard normal table) --------------------------------------------------------------------------------------------------------- 2. What is the probability that an Acme light bulb will last less than 300 days? P(X

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