1. QRB 501 Week 3 Exercise 4 Mean and variance A dusk-to-dawn outdoor lightbulb has an expected (mean) life of 8,000 hours with a standard deviation of 250 hours. How many bulbs in a batch of 500 can be expected to last no longer than 7,500 hours? To purchase this material click on the link http://www.assignmentcloud.com/QRB- 501-NEW/QRB-501-Week-3-Exercise-4 For more details visit www.assignmentcloud.com