Question

1. A study of the amount of time it takes a recording artist to record a CD shows that the mean is 11.2 hours with a standard deviation of 6.6 hours. If 40 recording artists are randomly selected, find the probability that their mean recording time is between 9.75 and 12.55 hours. Probability Statement:: ________________________ z-Score: ____________ Answer

Answer 1

Solution :

Given that,

mean = =11.2

standard deviation = =6.6

n =40

=11.2

₌ / n = 6.6 40 = 37.94733

P (9.75 < < 12.55 )

P ( 9.75 - 11.2 / 1.0435) < ( - / ) < ( 12.55 - 11.2  / 1.0435)

P ( - 1.7 / 1.0435< z < 1.35 /1.0435 )

P (-1.63 < z <1.29 )

P ( z < 1.29 ) - P ( z < -1.63 )

Using z table

= 0.9015 - 0.0516

= 0.8499

Probability = 0.8499