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1. Given a normal population whose mean is 50 and whose standard deviation is 5. Find the probability that a random sample of following number has A. A random sample of 4 B. A random sample of 16 C. A random sample of 25 2. Assume that the standard deviation increases as 10. A. Find the probability that a random sample of 4, 16, 25, respectively. 3. The following is the age of a random sample of eight men in a bar. This age is known to follow a normal distribution of 10 standard deviation. Get a 95% confidence interval estimate for the population mean. 52 68 22 35 30 56 39 48 4. The time required to replace the engine oil follows the normal distribution of 5 standard deviations. The oil exchange time of the random sample consisting of 10 oil exchange are recorded as follows. Get a 99% confidence interval estimate for the population mean. 11 10 16 15 18 12 25 20 18 24