The specific conductance (S/cm) is one measure of the salinity of prairie lakes and wetlands. In a

The specific conductance (μS/cm) is one measure of the salinity of prairie lakes and wetlands. In a specific wetland, a biogeochemical analysis suggests that the conductance is normally distributed with a mean of 2500 (μS/cm) with a standard deviation of 425 (μS/cm).

(a) What is the probability that a sample of 20 will yield a mean greater than 2600 (μS/cm)?

(b) What sample size would be needed to have sample mean within 100 (μS/cm) (assume z = 1.645)?