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

anonymous · Answer

Another z chart problem.  In this case, we need to find the number less than 1.9 sigma.  Probably about ninety-six percent.

anonymous · Answer

Actually, about 97.1% from the chart.