Question: Light bulbs are tested to see if they work or n ot. The probability of a bulb working properly is 0.8. 100 bulbs are checked.
a) What is the probability that exactly 92 bulbs work?
b) What is the probability that fewer than 80 bulbs work properly?
c) You now discover that there are two completely different machines which make the bulbs, Machine A and Machine B. How would this affect the assumptions which you made in calculating part a and b?
d) You are then told that (working) bulbs made by Machine A are used to light the main warehouse. Usually, one bulb burns out every 2 days. You are asked to calculate the probability that three bulbs will burn out in the space of one day.