A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period of time. Less than 690 hours

Question

A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period of time.	Less than 690 hours

amistre64 · Answer

without reading all the little words I believe this is simply an application of the z= stuff

amistre64 · Answer

$$z=\frac{x-\bar x}{\sigma}$$
$$P(z<690)\frac{690-500}{100}$$

amistre64 · Answer

6.9-5 = 1.9

look up in the ztable for the spot 1.9; .00

amistre64 · Answer

if i was smater I would have seen the to use the sd as a ruler would get me 19 times to get from 500 to 690 :)

amistre64 · Answer

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