Hi, i have this question wrong in my intro statistics class and i'm wonder if someone could help me understand why. Thanks in advance. Heres the question: "A string of christmas lights contains 4 bulbs. The lights are wired in a series, so that if one fails, the whole sting would go dark. Each light has a probability of 0.05 of failing in a 3-year period. The lights fail independently of each other. What is the probability that a sting of lights will fail in a 3 year period?" Now, my answer was 0.20, because each lights fail independetnly of each other, so then, if one fails, the others do not get a chance to fail. Since logically, w/o any external influence, a light bulb should not fail if it is not lit, therefore, 4 x .05 = 0.20. But i got the asnwer wrong, can someone help me to understand if i'm missing something? Thanks On another note, can more than one light in a series circuit burn out at the same time?