Ariel is studying when pine trees should be harvested for lu…

Ariel is studying when pine trees should be harvested for lumber and replanted. She learns that the Southern Yellow Pine has an average height of 90 ft, and its height is normally distributed with a standard deviation of 4 ft. What proportion of Southern Yellow Pines are more than 95 feet tall?

Suppose that I want to estimate the proportion of Americans…

Suppose that I want to estimate the proportion of Americans that prefer coffee to tea. If I don’t know anything about what this proportion may be in advance, how many people should I include in my study so that I have a 3% margin of error with 95% confidence?