Question

You will upload one file to answer questions 7-9.

7. The time it takes a randomly selected job applicant to perform a certain task has a distribution that can be approximated by a normal distribution with a mean of 120 seconds and a standard deviation of 20 seconds.

a. Find the probability that a randomly selected job applicant performs the task in more than 140 seconds. Use Excel to find your answer (upload the file). Round your answer to 4 decimal places. Is it likely that an applicant would take more than 140 seconds to perform a task?

b. The fastest 10% are to be given advanced training. What task time qualifies individuals for such training? (Remember the fastest times takes the least amount of time.) Use Excel to find your answer (upload the file). Round your answer to the nearest second.  

Answer 1

a. the probability that a randomly selected job applicant performs the task in more than 140 seconds

Excel :

Mean μ=	120
Standard deviation σ=	20
P ( X>140 )
X	140
Z	(x−μ)/σ
Z	1	(B5-B1)/B2
P (Z<1)	0.8413447	NORMSDIST(1)
P (Z>1)	0.1586553	1-B8
P ( X>140 )	0.1586553

b. The fastest 10% are to be given advanced training and task time qualifies individuals for such training

P(Z < -1.28) = 0.1

So , time = μ - 1.28*σ

= 120 - 1.28*20 = 94.4 seconds

Excel :

=NORMINV(0.1,120,20)

=94.36896869

=94.4