Question

In a certain country, the average age is 31 years old and the standard deviation is 4 years. If we select a simple random sample of 100 people from this country, what is the probability that the average age of our sample is at least 32?

0.006

0.599

0.401

0.994

Answer 1

Solution :

Given that ,

mean = = 31

standard deviation = = 4

n = 100

= 31

= / n = 4 / 100 = 0.4

P( ) = 1 - P( < 32)

= 1 - P[( - ) / < (32 - 31) / 0.4]

= 1 - P(z < 2.5)

= 0.006