Probability questions...

[albertlee]

1) what's the difference between:

something is supplied by R, given that it fails during the warranty period

and

something is supplied by R, and it fails during the warranty period

??

 

 

2) What's the definition of conditional probability? the def I found is:

This is the probability of an event given (or conditional upon) the occurrence of another event, eg the probability of disease Y given exposure to factor X.

can any explain this with a real life example?

 

3) There are 15 balls, where 8 blue, 7 red. I draw 5 balls, replacing each ball after I draw it. I tell you that four of the five balls were blue. What then is the probability that the first two balls I drew were blue?

 

4) A manufacturer of dishwashers uses electric pumps from three suppliers, P, Q and R, in the ratios 5:3:2 respectively. Of the pumps from supplier P 8% fail during the warranty period. The corresponding figures for the pumps supplied by Q and R are 10% and 5% respectively.

For two pumps chosen at random from those that fail during the warranty period, calculate the probability that they come from the same supplier.

 

For question 4), I have attempted to solve and come up with an answer. However, the question does not inform us the actually number of pumps, instead only ratio; wherefrom, I discover that if I use ratio as a real amount of pumps to calculate permutations/combinations, the probability can change when I multiply the ratio by a constant....so there must be something wrong here with ratio and probability...

 

 

Any way, this is not a course work or any thing. I just rewrite the questions from my books.

 

Please help me on 4 of the questions.

 

thanks