# Math Help - probability

1. ## probability

I calculated that 0.258 is the probability that you will detect an error on the first move.
So is this how to calculuate the probability that the move would be detected on the first or second sample taken after the move :

0.258 + (1-0.258)x(0.258)
= 0.449436

2. Originally Posted by Dgphru
I calculated that 0.258 is the probability that you will detect an error on the first move.
So is this how to calculuate the probability that the move would be detected on the first or second sample taken after the move :

0.258 + (1-0.258)x(0.258)
= 0.449436

Please post all of the question.

3. Ok well the question is:

A process is being controlled with a fraction nonconforming chart. The process average is 0.07. The procedure calls for taking samples of 400 items.

a) If the process average shifts to 0.10, what is the probability that the shift will be detected on the first subsequent shift?
b) What is the probability that the shift in part a) would be detected on the first or second sample taken after the shift.

I have already calculated a): standard deviation = 0.0128, and the upper control limit = 0.1083 and lower control limit = 0.0317
then i used the normal distibution to calculate the change from 0.07 to 0.10
and i got 0.258

but I'm just stuck on how to complete b).