An agricultural economist is interested in determining the a

An agricultural economist is interested in determining the average diameter of peaches produced by a particular tree. A random sample n = 30 peaches is taken and the sample mean is calculated. Suppose that the average diameter of peaches in this tree is known for previous years\' production to be = 60 millimeters with = 10mm. What is the probability that the sample mean exceeds 65 millimeters?

Solution

I guess s.d=10 mm..right?
x= sample mean..
previous years\' mean = 60 and s.d=10..

then,P( x > 65 ) = p( z > (65-60) / ( 10/sqrt(30) ) =p( z> 2.738612788 ) = 1- p(z<2.738612788)= 0.00308495