The contents of bottles of water have a distribution with me

The contents of bottles of water have a distribution with mean 9.1 ounces and standard deviation .3 ounce. Suppose a sample of size 64 will be taken and the sample mean will be calculated. What is the probability that a single bottle of water contains more than 9 ounces?

Solution

We first get the z score for the critical value. As z = (x - u) / s, then as          
          
x = critical value =    9      
u = mean =    9.1      
          
s = standard deviation =    0.3      
          
Thus,          
          
z = (x - u) / s =    -0.333333333      
          
Thus, using a table/technology, the right tailed area of this is          
          
P(z >   -0.333333333   ) =    0.63055866 [answer]