(1). Ball bearings from a production line have a mean diameter of 2.54 cm with a standard deviation of 0.2 cm. What is the probability that a random sample of 64 ball bearings has a an average diameter of more than 2.55 cm?

(2). Researchers at the Massachusetts General Hospital published in The New England Journal of Medicine that the distribution of albumin levels in cerebrospinal fluid is symmetric with mean 29.5 mg/100 ml and standard deviation 9.25 mg/100 ml. in American adults. If a random sample of 30 adults is taken, what is the probability that the sample mean is between 28 and 30 mg/100 ml?

(3). Samples are to be taken from a random variable X which is normally distributed with standard deviation equal to 5. Find the size of the sample needed so that the sample mean is within 1 unit of the population average with probability 0.90.

Answer rating: 100% (QA)

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