Question

Suppose that the hours of music that a person listens to per day is normally distributed with a mean of 4 hours with a standard deviation of 3.25 hours. If 9 people are selected at random, what is the probability that their average hours of listening to music will be less than 6 hours?

	a.	0.2676
	b.	0.0322
	c.	0.9678
	d.	0.7324

Answer 1

Solution :

mean = = 4

standard deviation = = 3.25

n = 9

= = 4

= / n = 3.25 / 9 = 1.0833

P( < 6 ) = P(( - ) / < (6 -4) /1.0833 )

= P(z < 1.85)

= 0.9678

probability = 0.9678

Answer = C. 0.9678