Q1.

Suppose that the lifetimes of TV tubes are normally distributed with a standard deviation of 1.1

years. Suppose also that exactly 20% of the tubes die before 4.5 years. Find the mean lifetime of TV tubes. Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place.

... years

Q2.

The control department of a light bulb manufacturer randomly picks 4400 light bulbs from the production lot every week. The records show that, when there is no malfunction, the defect rate in the manufacturing process (due to imperfections in the material used) is 1%. When 1.25% or more of the light bulbs in the sample of 4400 are defective, the control unit calls repair technicians for service. Answer the following. (If necessary, consult a list of formulas.) A A (a) Find the mean of p, where p is the proportion of defective light bulbs in a sample of 4400 when there is no X b O malfunction. . l] A (b) Find the standard deviation ofp. D A (c) Compute an approximation for P(p 2 0.0125), which is the probability that the service technicians will be called even though the system is functioning properly. Round your answer to four decimal places. [1 Withdrawal symptoms may occur when a person using a painkiller suddenly stops using it. For a special type of painkiller, withdrawal symptoms occur in 2% of the cases. Consider a random sample of 1600 people who have stopped using the painkiller. Answer the following. (If necessary, consult a list of formulas.) A A (a) Find the mean of p, where p is the proportion of people in the sample who experience withdrawal symptoms. I] A (b) Find the standard deviation ofp. I] A (c) Compute an approximation for P(p