last one...
the time that customers take to complete their transaction at a money machine is a random variable with mean=2 minutes and standard deviation=0.6 minute. Find the probablilty that a random sample of 50 customers will take between 90 and 112.5 minutes to complete all their transactions. That is, find the probability that X(with line over it) will be between 1.8 and 2.25 minutes.
thanks. i'm trying it on my own but i want to see if i get it right
2007-04-17 14:51:54 · 1 answers · asked by trackgirl000 2 in Science & Mathematics ➔ Mathematics
(b) find the probability that the total time it takes the 50 customers is less than 95 minutes
2007-04-17 14:56:59 · update #1
Probably, you also assume the distriubtion is normal.
Go to the friendly z-tables. 90 minutes/50 customers is 1.8 minutes, which is a z of -0.2/0.6= -1/3 and 112.5 min/50 customers or 2.25 minutes, which is a z of 0.25/0.6 = 0.417
Call the first result (culmative probability from - infinity to z= -1.3) = A. Call the second result (culmulative probabilty from - infinity to 0.417)= B
Your result is B-A.
2007-04-17 15:00:31 · answer #1 · answered by cattbarf 7 · 0⤊ 0⤋