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

kropot72 · Answer

$$z=\frac{X-\mu}{\sigma}=\frac{690-500}{100}=1.9$$
Now you need to refer to the standard normal distribution table to find the answer. Can you do that and post your answer back?