Question

The life expectancy in the United States is 75 years with a population standard deviation of 7 years. A random sample of 49 individuals is selected. What is the probability that the sample mean will be less than 72.5 years

Answer 1

Solution :

Given that ,

mean = = 75

standard deviation = = 7

n = 49

= 75

=  / n =7 / 49=1

P( < 72.5) = P[( - ) / < (72.5 -75) /1 ]

= P(z < -2.5)

Using z table  

= 0.0062

probability=0.0062