Time remaining:
help with statistics homework

Statistics
Tutor: None Selected Time limit: 0 Hours

Power+, Inc produces AA batteries used in remote controlled toy cars. The mean life of these batteries follows the normal probability with a mean of 37 hours and a standard deviation of 5.5 hours.

As a part of its quality assurance program Power+, Inc. tests sample of 9 batteries

a) What proportion of the sample will have a mean useful life greater than 36.5 hours ?

b) what proportion of the sample will have a mean useful life between 36.5 and 38.5hrs? (Round z value to 2 decimal places and final 4

Apr 12th, 2015

For sample means you have to divide the standard deviation by the square root of the sample number.

So, the sample standard deviation is 5.5 / √9 = 5.5 / 3 = 1.833

Then,

a) Z = 36.5-37 / 1.833 = -0.27

then p(36.5)  = 0.3936

b)  Z of 38.5 = 38.5-36.5 / 1.833 = 1.09

then p(38.5) = 0.8621

between 36.5 and 38.5 is

0.8621 - 0.3936 = 0.4685

Apr 12th, 2015

Oh, sorry, correct for a)

they want the proportion GREATER than 36.5

So then it's  1 - 0.3936 = 0.6064

Apr 12th, 2015

that's the correction for a)

Apr 12th, 2015

Are you studying on the go? Check out our FREE app and post questions on the fly!
Download on the
App Store
...
Apr 12th, 2015
...
Apr 12th, 2015
Dec 4th, 2016
check_circle
Mark as Final Answer
check_circle
Unmark as Final Answer
check_circle
Final Answer

Secure Information

Content will be erased after question is completed.

check_circle
Final Answer