Suppose that the distribution of the lifetime of a car battery produced by a certain car company is well approximated by a normal distribution with a mean of 1300 hours and variance 104. What is the approximate probability that a batch of 100 car batteries will contain at least 20 whose lifetimes are less than 1205 hours?

The shelf life of a perishable product is a random variable that is related to customer acceptance and, ultimately, to sales and profit. Suppose the shelf life of a particular soft drink is best approximated by a normal distribution with a mean of 180 days and standard deviation 20 days. What fraction of the product will still be fresh after 5 months on the shelf?

Assume that the square footage of a residential house in the US is normally distributed with a mean=1000 and standard deviation=150 square feet. If we select a random house what is the probability that it will be at most 1050 square feet?

For a standardized psychology examination intended for psychology majors, the historical data show that scores have a mean of 515 and a standard deviation of 170. The grading process of this year's exam has just begun. The mean score of the 35 exams graded so far is 518. What is the probability that a sample of 35 exams will have a mean score of 518 or more if the exam scores follow the same distribution as in the past? Carry your intermediate computations to at least four decimal places. Round your answer to at least three decimal places.

TREKLAIR bulbs have an average lifespan of800 hours with a variance of 1,600 hours2 .This duration oflife has a normal distribution. Find the probability that abulb lasts between 778 and 834 hours.

Suppose that the fraction of defective modems shipped by a data-communications vendor has an approximation beta distribution with a=5 and b=21. find the mean and variance of the fraction of defective modems per shipment What is the probability that a randomly selected shipment will contain at least 30 % defectives? What is the probability that a randomly selected shipment will contain no more than 5 % defectives?

A recent study was conducted and it found that IQ's are normally distributed with a mean of a 100 and a standard deviation of 15. 1. What is the probability that a randomly selected individual would have an IQ between 97 and 112 2. What is the probability that a randomly selected individual would have an IQ between 100 and 113 3. What is the probability that a randomly selected individual would have an IQ of less than 112 and greater than 115

The life span of a certain wood cutting machine manufactured by a factory has a normal distribution with a guarantee that any machine that stars malfunctioning within 36 months of the purchase will be replaced by a new one. How many percentages of machines are expected to be replaced in the following cases? Mean of 60 months and variance of 64 months2 Mean of 45 months and variance of 36 months2 Mean of 75 months and variance of 16 months2