The life span of a light bulb is normally distributed with a population standard deviation of 50 hours. A randomly selected sample of 25 bulbs had an average life span of 725 hours. (Call this the "original sample.")

10.Use the original sample to find the point estimate for the

population mean of the lifespan.

11.Assume the value of the population mean (?) is equal to the point

estimate found in Problem 10. Find the probability that the life span

of a randomly selected bulb will be between 722 and 738 hours.

12.Assume again that the population mean (?) is equal to the point

estimate found in Problem 10. Find the probability that the mean of

a randomly selected sample of 20bulbs will be between 722 and

728 hours.