Question

Suppose the distribution of weekly study times amoung Rutgers students has mean 20 hours and standard deviation 8 hours.

1. In a sample size of 75, determine the probability that the average study time is more than 18.5 hours. Write your answer as a decimal with 3 digits.

Answer 1

Solution :

Given that ,

mean = = 20

standard deviation = = 8

n = 75

= 20

= / n =8 / 75 = 0.9238

P( >18.5 ) = 1 - P( < 18.5)

= 1 - P[( - ) / < (18.5 -20) /0.9238 ]

= 1 - P(z <-1.62 )

Using z table

= 1 - 0.0526

= 0.9474

probability= 0.947