Question

Lightbulb lifetimes follow an unknown distribution, with a mean length of 10702 hours and a standard deviation of 325 hours. Suppose that a sample of 72 lightbulbs is taken. What is the probability that the total lifetime of these lightbulbs is less than 768751 hours? Select one O a We cannot answer this question with the information given. O b.0.6500 c. 1.0000 od 0 7421 0.0.2579

Answer 1

let x - lifetime of a single bulb. XN N (10702, 3252) n=72 1 11 we have to find, Total lifetime of these bulbs to be less than 768 751 hrs PC Ex; < 768751) 72 Xi ۲( < 768751 72 PCE (10677.1) 106771 10702 с Р ( Boy X-M olun 2252 P(Z <=0.65) 0.2579