Home Depot sells compact fluorescent lamps (CFLs) that have a mean life of 10,000 hours with a standard deviation of 1,000 hours. In an order of 8,000 lamps, how many can be expected to last 11,000 hours or longer?

Answer 1

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http://davidmlane.com/hyperstat/z_table.html
click on above

prob = .1587
multiply that by 8000

Answer 2

1587 x 8000 = 12696000