(solution) I need help understanding the problems i submitted to you Download Attachment:

(solution) I need help understanding the problems i submitted to you Download Attachment:

I need help understanding the problems i submitted to you Download Attachment: Document Preview: 0) A normal population has a mean of 20 and a standard deviation of 4.   Compute the z value associated with 25. =1.25 What proportion of the population is between 20 and 25? What proportion of the population is less than 18? 1) Assume that the hourly cost to operate a commercial airplane follows the normal distribution with a mean of $3,236 per hour and a standard deviation of $432. What is the operating cost for the lowest 5% of the airplanes? 3) A study of long-distance phone calls made from General Electric Corporate Headquarters in Fairfield, Connecticut, revealed the length of the calls, in minutes, follows the normal probability distribution. The mean length of time per call was 4.50 minutes and the standard deviation was 0.70 minutes. A)What fraction of the calls last between 4.50 and 5.30 minutes? B) What fraction of the calls last more than 5.30 minutes? C) What fraction of the calls last between 5.30 and 6.00 minutes? D) What fraction of the calls last between 4.00 and 6.00 minutes? E) As part of her report to the president, the director of communications would like to report the length of the longest (in duration) 5 percent of the calls. What is this time? 3) The mean age at which men in the United States marry for the first time follows the normal distribution with a mean of 24.1 years. The standard deviation of the distribution is 2.5 years. A) For a random sample of 66 men, what is the likelihood that the age at which they were married for the first time is less than 24.6 years?     2) Assume that the hourly cost to operate a commercial airplane follows the normal distribution with a mean of $3,236 per hour and a standard deviation of $432.  What is the operating cost for the lowest 5% of the airplanes?