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October 1, 2014

October 1, 2014

Posted by **br0Ok3** on Friday, October 15, 2010 at 1:15am.

TKK Products manufactures electric light bulbs in the 50-, 60-, 75-, and 100-watt range. Laboratory tests show that the lives of these light bulbs are normally distributed with a mean of 774 hr and standard deviation of 68 hr. Find the probability that a TKK light bulb selected at random will burn for the following times. Round your standard normal variable to two decimal places before using the table of values. (Give your answers to four decimal places.)

(a) less than 842 hr

(b) between 842 and 910 hr

(c) more than 638 hr

- statistics -
**PsyDAG**, Saturday, October 16, 2010 at 12:09pmZ = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions for the Z scores you obtain.

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