Question

The average age of US adult males is 69.5 inches with a standard deviation of 4.1 inches. An SRS of 13 adult US males was selected. What is the approximate probability that their average height is less than 71 inches?

Answer 1

Solution :

Given that ,

mean = = 69.5

standard deviation = = 4.1

n = 13

= 69.5 and

= / n = 4.1 / 13  

P( < 71) = P(( - ) / < (71 - 69.5) / 4.1 / 13  )

= P(z < 1.32)

Using standard normal table,

P( < 71) = 0.9066

Probability = 0.9066