Economics and Finance Along with gold and silver, platinum is also considered a precious metal and is traded on the commodities market. A random sample of the price of platinum (in dollars per troy ounce) was obtained from jewelers around the world. The resulting summary statistics were x‾ = 664.50, σ = 5.25, and n = 55. Assume the underlying distribution of the price is normal.
a. Find a 95% confidence interval for the current true mean price per troy ounce of platinum.
b. One month ago, a brokerage firm reported the true mean price of platinum to be $660.79 per troy ounce, with a recommendation to buy. Is there any evidence to suggest the true mean price has increased? Justify your answer.