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Exercise. Let Dbe a normally distributed random variable with mean 303 and standard deviation 24. Let H=D' be the variable corresponding to averaging 100 independent copies of D. A. Must Hbe a normal variable? B. Find the mean and standard deviation of H. Exercise. At a warehouse, the effort needed to process an order is measured in worker-minutes (that is, combined time invested by all workers on the one job), abbreviated w-min. Experience suggests that the distribution of effort perjob is roughly 66.4 w~min, with a standard deviationof 15.1. At the start of a day, the warehouse receives 40job orders. A. Find a 95% condence interval for the average effort expected over the 40 jobs. B. Find a 95% condence interval for the total effort required for all jobs. Exercise T-stat. To understand a random variable W, a surveyer reviews 24 readings. The list has an average of 182, and a sample standard deviation of 13. Assume the variable is normally distributed. The surveyer wants a 95% condence for the mean of W. A. What are the appropriate values of df (degrees of freedom) and t* for this calculation? B. Enter, to the nearest tenth, the bounds for this condence interval