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davidmlane.com/hyperstat/z_table.html
The amount of time a certain brand of light bulb lasts is normally distribued with a mean of 1300 hours and a standard deviation of 60 hours. Out of 710 freshly installed light bulbs in a new large building, how many would be expected to last between 1240 hours and 1430 hours, to the nearest whole number?
1 answer