Chapter 7. page 303

  1. A company buys 100 lightbulbs, each of which has an exponential lifetime of 1000 hours. What is the expected time for the first of these bulbs to burn out? (See Exercise 10.)

Answer:

Here, Total lightbulbs (n) = 100 lifetime (mean)= 1000 hours

Therefore, the total expected time for the first of these bulbs to burn out = mean / n = 1000 hrs / 100 = 10 hrs.