Posted by **amelie** on Sunday, April 20, 2008 at 7:09pm.

For the sheet-metal stamping machine in a certain factory, the time between failures, X1 has a mean between the failures, of 56 hours and a variance of 16 hours. The prepair time X2, has a mean time to repair of 5 hours and a variance of 4 hours.

a) If X1 and X2 are independent , find

the expected value and the variance

of Y=X1+X2, which represents one

operation-repair cycle.

b)Would you expect an operation-repair

cycle to last more than 75 hours?Why?

Work

------------------------

a) E(Y)= E(X1+X2)= EX1+EX2= 56+5=61

V(Y)= ... = 20

b) P(Y>75) = P(X1+X2 >75) =

I'm not sure where to go from here, i thought of using complement but i just got stuck.

ans: no, P(Y>75)<=0.1653

## Answer this Question

## Related Questions

- probability - The life of a certain type of device has an advertised failure of ...
- Statistics - A modification is made to a computer component to try to increase ...
- statistics - The duration of time it takes General Motors to build a car is ...
- Statistics - An industrial engineer has found that the standard household light ...
- Quantitative Techniques - Q No. A company is seriously considering buying one ...
- stats - a study of the amount of time it takes a mechanic to rebuild the ...
- Stats - In the past, the mean running time for a certain type of flashlight ...
- Statistics - A survey among freshmen at a certain university revealed that the ...
- math - Suppose that the time (in hours) required to repair a machine is an ...
- Keith - The Information Systems Audit and Control Association surveyed office ...

More Related Questions