Question

The weight of a tool manufactured by a tool maker follows a normal distribution with a mean of 8kg and a standard deviation of 1.5kg.

For quality control, the Production manager was rejecting any manufactured tool weighing under 6.5 kg. Calculate the approximate percentage of rejected tools.

	A.	10%
	B.	16%
	C.	20%
	D.	25%
	E.	13%

Answer 1

Solution:

Given, X follows Normal distribution with,

   = 8

= 1.5  

Now ,

P(X < 6.5)

= P[(X - )/ <  (6.5 - )/]

= P[Z <  (6.5 - 8)/1.5]

= P[Z < -1.00]

= 0.1587 ... ( use z table)

= 15.87%

= 16% nearly

Answer : 16%

  

Find P(X > )