light bulbs are measured in lumens (light output), watts (energy used), and hours (life). a standard white light bulb has a mean life of 675 hours and a standard deviation of 50 hours. a soft white light bulb has a mean life of 700 hours and a standard deviation of 35 hours. at a local science competition, both light bulbs lasted 750 hours. which light bulb's life span was better?
